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rfc:rfc2879

Network Working Group G. Klyne Request for Comments: 2879 Content Technologies Obsoletes: 2531 L. McIntyre Category: Standards Track Xerox Corporation

                                                             August 2000
            Content Feature Schema for Internet Fax (V2)

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

 This document defines a content media feature schema for Internet
 fax.
 It is a profile of the media feature registration mechanisms [1,2,3]
 for use in performing capability identification between extended
 Internet fax systems [5].  It replaces and updates the feature schema
 defined in RFC 2531.

Table of Contents

 1. Introduction .............................................2
    1.1 Organization of this document ........................3
    1.2 Terminology and document conventions .................3
    1.3 Discussion of this document ..........................4
 2. Fax feature schema syntax ................................4
 3. Internet fax feature tags ................................4
    3.1 Image size ...........................................5
    3.2 Resolution ...........................................5
    3.3 Media type ...........................................6
    3.4 Paper Size ...........................................6
    3.5 Color capability .....................................7
    3.6 Color model ..........................................8
    3.7 Image coding ........................................11
    3.8 MRC mode ............................................12
 4. Examples ................................................13
    4.1 Simple mode Internet fax system  ....................13

Klyne & McIntyre Standards Track [Page 1] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

    4.2 High-end black-and-white Internet fax system.........14
    4.3 Grey-scale Internet fax system ......................14
    4.4 Full-color Internet fax system (JPEG only) ..........15
    4.5 Full-color Internet fax system (JPEG and JBIG) ......16
    4.6 Full-color Internet fax system (MRC) ................17
    4.7 Sender and receiver feature matching ................19
 5. IANA Considerations .....................................21
 6. Security Considerations .................................21
    6.1 Capability descriptions and mechanisms ..............21
    6.2 Specific threats ....................................21
 7. Acknowledgements ........................................22
 8. References ..............................................22
 9. Authors' Addresses ......................................24
 Appendix A: Feature registrations ..........................25
    A.1 Image size ..........................................25
    A.2 Resolution aspect ratio .............................27
    A.3 Color levels ........................................28
    A.4 Color space  ........................................30
    A.5 CIELAB color illuminant .............................33
    A.6 CIELAB color depth ..................................35
    A.7 CIELAB color gamut ..................................37
    A.8 Image file structure ................................39
    A.9 Image data coding ...................................41
    A.10 Image coding constraint ............................43
    A.11 JBIG stripe size .................................. 44
    A.12 Image interleave ...................................46
    A.13 Color subsampling ..................................47
    A.14 MRC availability and mode ..........................49
    A.15 MRC maximum stripe size ............................50
 Appendix B: TIFF mode descriptions .........................52
 Appendix C: Changes from RFC 2531 ..........................57
 Full Copyright Statement ...................................58

1. Introduction

 This document defines a content media feature schema for Internet
 fax.
 It is a profile of the media feature registration mechanisms [1,2,3]
 for use in performing capability identification between extended
 Internet fax systems [5].  It replaces and updates the feature schema
 defined in RFC 2531.
 The media feature description mechanisms do not describe any specific
 mechanisms for communicating capability information, but do presume
 that any such mechanisms will transfer textual values.  In
 conjunction with this feature schema, they specify a textual format
 to be used for describing Internet Fax capability information.

Klyne & McIntyre Standards Track [Page 2] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

 The range of capabilities that can be indicated are based on those
 covered by the TIFF file format for Internet fax [7] and Group 3
 facsimile [6].  A companion document [4] describes the relationship
 and mapping between this schema and Group 3 fax capabilities.

1.1 Organization of this document

 Section 2 specifies the overall syntax for fax feature descriptions
 by reference to the media feature registration and syntax documents
 [1,2].
 Section 3 enumerates the feature tags that are to be recognized and
 processed by extended Internet fax systems, according to their
 capabilities.
 Appendix A contains additional feature tag registrations for media
 features that are specific to fax and for which no applicable
 registration already exists.  These are presented in the form
 prescribed by the media feature registration procedure [1].

1.2 Terminology and document conventions

 The term "extended Internet fax system" is used to describe any
 software, device or combination of these that conforms to the
 specification "Extended Facsimile Using Internet Mail" [5].
 "capability exchange" describes any transfer of information between
 communicating systems that is used to indicate system capabilities
 and hence determine the form of data transferred.  This term covers
 both one-way and two-way transfers of capability information.
 "capability identification" is a particular form of capability
 exchange in which a receiving system provides capability information
 to a sending system.
 "capability description" is a collection of data presented in some
 specific format that describes the capabilities of some communicating
 entity.  It may exist separately from any specific capability
 exchange mechanism.
      NOTE:  Comments like this provide additional nonessential
      information about the rationale behind this document.
      Such information is not needed for building a conformant
      implementation, but may help those who wish to understand
      the design in greater depth.

Klyne & McIntyre Standards Track [Page 3] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

1.3 Discussion of this document

 Discussion of this document should take place on the Internet fax
 mailing list hosted by the Internet Mail Consortium (IMC).  Please
 send comments regarding this document to:
     ietf-fax@imc.org
 To subscribe to this list, send a message with the body 'subscribe'
 to "ietf-fax-request@imc.org".
 To see what has gone on before you subscribed, please see the mailing
 list archive at:
     http://www.imc.org/ietf-fax/

2. Fax feature schema syntax

 The syntax for the fax feature schema is described by "A syntax for
 describing media feature sets" [2].  This in turn calls upon media
 feature tags that may be registered according to the procedure
 described in "Media Feature Tag Registration Procedure" [1].
      NOTE:  Media feature registration provides a base
      vocabulary of features that correspond to media handling
      capabilities.  The feature set syntax provides a
      mechanism and format for combining these to describe
      combinations of features.  This memo indicates those
      features that may be associated with extended Internet
      fax systems.

3. Internet fax feature tags

 This section enumerates and briefly describes a number of feature
 tags that are defined for use with extended Internet fax systems and
 applications.  These tags may be used also by other systems and
 applications that support corresponding capabilities.
 The feature tags presented below are those that an extended Internet
 fax system is expected to recognize its ability or non-ability to
 handle.
 Definitive descriptions of feature tags are indicated by reference to
 their registration according to the media feature registration
 procedure [1] (some of which are appended to this document).

Klyne & McIntyre Standards Track [Page 4] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

      NOTE:  The presence of a feature tag in this list does
      not mean that an extended Internet fax system must have
      that capability;  rather, it must recognize the feature
      tag and deal with it according to the capabilities that
      it does have.
      Further, an extended Internet fax system is not prevented
      from recognizing and offering additional feature tags.
      The list below is intended to provide a basic vocabulary
      that all extended Internet fax systems can use in a
      consistent fashion.
      If an unrecognized or unused feature tag is received, the
      feature set matching rule (described in [2]) operates so
      that tag is effectively ignored.

3.1 Image size

 Feature tag name    Legal values
 ----------------    ------------
 size-x              <Rational> (>0)
 size-y              <Rational> (>0)
 Reference:  this document, Appendix A.
 These feature values indicate a rendered document size in inches.
 Where the actual size is measured in millimetres, a conversion
 factor of 10/254 may be applied to yield an exact inch-based value.

3.2 Resolution

 Feature tag name    Legal values
 ----------------    ------------
 dpi                 <Integer> (>0)
 dpi-xyratio         <Rational> (>0)
 Reference: "Media Features for Display, Print, and Fax" [3], and this
 document appendix A.
 If 'dpi-xyratio' is present and not equal to 1 then the horizontal
 resolution (x-axis) is indicated by the 'dpi' feature value, and the
 vertical resolution (y-axis) is the value of 'dpi' divided by 'dpi-
 xyratio'.

Klyne & McIntyre Standards Track [Page 5] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

 For example, the basic Group 3 fax resolution of 200*100dpi might be
 indicated as:
    (& (dpi=200) (dpi-xyratio=200/100) )
 When describing resolutions for an MRC format document, the complete
 set of usable resolutions is listed.  However, there are some
 restrictions on their use:  (a) 100dpi resolution can be used only
 with multi-level images, and (b) any multi-level image resolution is
 required to be an integral sub-multiple of the applicable mask
 resolution.

3.3 Media type

 Feature tag name    Legal values
 ----------------    ------------
 ua-media            screen
                     screen-paged
                     stationery
                     transparency
                     envelope
                     envelope-plain
                     continuous
 Reference: "Media Features for Display, Print, and Fax" [3].
      NOTE: Where the recipient indicates specific support for
      hard copy or soft copy media type, a sender of color
      image data may wish to adjust the color components (e.g.
      per the related rules of ITU recommendation T.42 [9]) to
      improve rendered image quality on that medium.

3.4 Paper Size

 Feature tag name    Legal values
 ----------------    ------------
 paper-size          A4
                     A3
                     B4
                     letter
                     legal
 Reference: "Media Features for Display, Print, and Fax" [3].

Klyne & McIntyre Standards Track [Page 6] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

3.5 Color capability

 Feature tag name    Legal values
 ----------------    ------------
 color               Binary  (bi-level only)
                     Limited (a limited number of colors)
                     Mapped  (palette or otherwise mapped color)
                     Grey    (grey-scale only)
                     Full    (full continuous-tone color)
 Reference: "Media Features for Display, Print, and Fax" [3].
 The intention here is to give a broad indication of color handling
 capabilities that might be used, for example, to select among a small
 number of available data resources.
 The value of this feature also gives an indication of the more
 detailed color handling features that might be applicable (see next
 section).
 'Binary' indicates blank-and-white, or other bi-level capability.  No
 further qualifying feature tags are required.
 'Limited' indicates a small number of distinct fixed colors, such as
 might be provided by a highlight printer, pen plotter or limited
 color display.  The 'color-levels' tag should be used to indicate the
 number of distinct colors available.
      NOTE:  No ability to indicate any specific or named color
      is implied by this option.  Some devices might use
      different intensity levels rather than different hues for
      distinction.
 In the context of Internet fax, 'limited' is interpreted as one-bit-
 per-color-sample (RGB, CMY or CMYK), depending on the color space
 used.
 'Mapped' indicates that pixel color values are mapped in some
 specifiable way to a multi-component color space.  The 'color-levels'
 tag may be used to indicate the number of distinct colors available;
 in its absence, sufficient levels to display a photographic image
 should be assumed.
 'Grey' indicates a continuous tone grey-scale capability.
 'Full' indicates full continuous tone color capability.

Klyne & McIntyre Standards Track [Page 7] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

 For 'Mapped', 'Grey' and 'Full' color, additional feature tags
 (section 3.6) may be used to further qualify the color reproduction.

3.6 Color model

 Feature tag name    Legal values
 ----------------    ------------
 color-levels        <integer>   (>2)
 color-space         Device-RGB  (device RGB)
                     Device-CMY  (device CMY)
                     Device-CMYK (device CMYK)
                     CIELAB      (LAB per T.42 [9])
                     (may be extended by further registrations)
 color-illuminant    <token>     (per ITU T.4 [13], E.6.7)
                     D50
                     D65
                     D75
                     SA
                     SC
                     F2
                     F7
                     F11
                     CTnnnn      (see below)
 CIELAB-L-depth      <integer>   (>0)
 CIELAB-a-depth         "
 CIELAB-b-depth         "
 CIELAB-L-min        <integer>
 CIELAB-L-max           "
 CIELAB-a-min           "
 CIELAB-a-max           "
 CIELAB-b-min           "
 CIELAB-b-max           "
 Reference: this document, appendix A.
 The general model for image handling (both color and non-color) is
 described here from a receiver's perspective;  a similar model
 operates in the reverse direction for a scan/send perspective:
      raw bit        pixel         color         physical
      stream  -(A)-> values -(B)-> values -(C)-> rendition
  1. "raw bit stream" is a stream of coded bits
 (A)  indicates image coding/decoding (MH,MR,MMR,JPEG,JBIG,etc.)
  1. "pixel values" are a single numeric value per picture element

that designates the color of that element.

Klyne & McIntyre Standards Track [Page 8] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

 (B)  indicates pixel-to-color value mapping
  1. "color values" have a separate numeric value for each color

component (i.e. L*, a*, b* in the case of CIELAB indicated

      above.)
 (C)  indicates how the color values are related to a physical
      color.  This involves interpretation of the color value with
      respect to a color model (e.g. RGB, L*a*b*, CMY, CMYK) and a
      color space (which is typically recipient-dependent).
  1. "physical rendition" is a color value physically realized on a

display, printer or other device.

 There are many variables that can be applied at each stage of the
 processing of a color image, and any may be critical to meaningful
 handling of that image in some circumstances.  In other circumstances
 many of the variables may be implied (to some level of approximation)
 in the application that uses them (e.g. color images published on a
 Web page).
 The color feature framework described here is intended to allow
 capability description at a range of granularity:  feature tags which
 correspond to implied (or "don't care" or "unknown") feature values
 may simply be omitted from a capability description.
 Grey scale and bi-level images are handled within this framework as a
 special case, having a 1-component color model.  The following
 features are used for describing color capabilities:
 'color-levels' indicates the number of distinct values for each
 picture element, and applies to all but bi-level images.  For bi-
 level images, a value of 2 is implied.
 'color-space' is used mainly with 'Mapped' and 'Full', but could be
 used with other modes if the exact color or color model used is
 significant.  Two kinds of color space can be distinguished:
 device-dependent and calibrated.  Device dependent spaces are named
 here as 'Device-xxx', and are used to indicate a color space that is
 defined by the receiving device.  Calibrated color spaces presume the
 existence of a rendering system that is calibrated with respect to an
 indicated definition, and is capable of processing the device-
 independent color information accordingly.

Klyne & McIntyre Standards Track [Page 9] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

 A color-handling receiver should indicate any appropriate device
 color space capability in addition to any calibrated color spaces
 that it may support.  A calibrated color space should be used when
 precise color matching is required in the absence of specific
 knowledge of the receiving system.
   NOTE:  In practice, although they appear to be separate
   concepts, the color model and color space cannot be
   separated.  In the final analysis, a color model (RGB,
   CMY, etc.) must be defined with respect to some color
   space.
 'color-illuminant' indicates a CIE illuminant, using the same general
 form that is used for this purpose by Group 3 fax (as defined in ITU
 T.4 [13], section E.6.7).  When the illuminant is specified by its
 color temperature, the token string 'CTnnnn' is used, where 'nnnn' is
 a decimal number that is the color temperature in Kelvins; e.g.
 CT7500 indicates an illuminant color temperature of 7500K.
   NOTE: ITU T.4 indicates a binary representation for color
   temperature values.
   In practice, much of the illuminant detail given here
   will probably be unused by Internet fax.  The only value
   likely to be specified is 'D50', which is the default
   color illuminant for Group 3 fax.
 'CIELAB-L-depth', 'CIELAB-a-depth' and 'CIELAB-b-depth' indicate the
 number of different values that are possible for the L*, a* and b*
 color components respectively, and are significant only when colors
 are represented in a CIELAB color space.  These features would be
 used with palletized color, or with full color where each color
 component has a different number of possible values.
 Color depth values relate to the representation of colour values
 rather than the resolution of a scanning or rendering device.  Thus,
 if 256 different L-component values can be represented then the
 assertion (CIELAB-L-depth<=256) is used, even if a receiving device
 can render only 100 distinct luminance values.  (Color rendering
 resolution is not covered by this memo.)
 The 'CIELAB-x-min' and 'CIELAB-x-max' values indicate a color gamut
 (i.e. a range of color values that are used or may be rendered).  A
 gamut may be indicated in terms of the CIELAB color space even when
 colors are represented in some other space.

Klyne & McIntyre Standards Track [Page 10] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

3.7 Image coding

 Feature tag name    Legal values
 ----------------    ------------
 image-file-         TIFF
 structure           TIFF-limited
                     TIFF-minimal
                     TIFF-MRC
                     TIFF-MRC-limited
                     (may be extended by further registrations)
 image-coding        MH
                     MR
                     MMR
                     JBIG
                     JPEG
                     (may be extended by further registrations)
 image-coding-       JBIG-T85    (bi-level, per ITU T.85)
 constraint          JBIG-T43    (multi-level, per ITU T.43)
                     JPEG-T4E    (per ITU T.4, Annex E)
                     (may be extended by further registrations)
 JBIG-stripe-size    <Integer>
 image-interleave    Stripe
                     Plane
 color-subsampling   "1:1:1"     (no color subsampling)
                     "4:1:1"     (4:1:1 color subsampling)
 Reference: this document, appendix A.
 'image-file-structure' defines how the coded image data is wrapped
 and formatted.  The following options are defined here:
 o  'TIFF' indicates image data enclosed and tagged using TIFF
    structures described in Adobe's definition of TIFF [20].
 o  'TIFF-limited' indicates image data structured using TIFF, but
    with the limitations on the placement of Image File Descriptors
    (IFDs) indicated in section 4.4.6 of RFC 2301 [7].
 o  'TIFF-minimal' indicates a TIFF image format that meets the IFD
    placement, byte ordering and bit ordering requirements of the
    "minimal black and white mode" described in section 3.5 of RFC
    2301 [7], also known as TIFF-S.
 o  'TIFF-MRC' uses a TIFF image structure [20] augmented with a sub-
    IFD structure, described for the "Mixed Raster Content mode" in
    section 8.1.2 of RFC 2301 [7], also known as TIFF-M.  This
    provides a file structure to contain composite images constructed
    using the MRC model described in T.44 [15] (see tag 'MRC-mode').

Klyne & McIntyre Standards Track [Page 11] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

 o  'TIFF-MRC-limited' is the same as 'TIFF-MRC', except that the
    primary IFD (i.e. top-level IFDs, as opposed to sub-IFDs)
    placement is constrained in the same way as 'TIFF-limited'.
 'image-coding' describes how raw image data is compressed and coded
 as a sequence of bits.  These are generic tags that may apply to a
 range of file formats and usage environments.
 'image-coding-constraint' describes how the raw image data coding
 method is constrained to meet a particular operating environment.
 Options defined here are JBIG and JPEG coding constraints that apply
 in typical Group 3 fax environments.
 The 'JBIG-stripe-size' feature may be used with JBIG image coding,
 and indicates the number of scan lines in each stripe except the last
 in an image.  The legal constraints are:
    (JBIG-stripe-size=128)
    (JBIG-stripe-size>=0)
 The latter being equivalent to no restriction.
   NOTE: there are several image coding options here, and
   not all are required in all circumstances.
   Specification of the image-file-structure tag value alone
   is not normally sufficient to describe the capabilities
   of a recipient.  A general rule is that sufficient detail
   should be provided to exclude any unsupported features.
   For extended Internet fax, image-file-structure and
   image-coding should always be specified, together with
   additional values described above as needed to clearly
   indicate which feature tag values are supported and which
   are not.  (See also the examples in section 4.)

3.8 MRC mode

 Feature tag name    Legal values
 ----------------    ------------
 MRC-mode            <Integer> (0..7)   (per ITU T.44 [15])
 MRC-max-stripe-size <Integer>
 Reference: this document, appendix A.

Klyne & McIntyre Standards Track [Page 12] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

 The 'MRC-mode' feature is used to indicate the availability of MRC
 (mixed raster content) image format capability.  A zero value
 indicates MRC is not available, a non-zero value indicates the
 maximum available MRC mode number.
 An MRC formatted document is actually a collection of several images,
 each of which is described by a separate feature collection.  An
 MRC-capable receiver is presumed to be capable of accepting any
 combination of contained images that conform to both the MRC
 construction rules and the image-coding capabilities declared
 elsewhere.
 Within an MRC-formatted document, multi-level coders are used for
 foreground and background images (i.e. odd-numbered layers: 1, 3, 5,
 etc.) and bi-level coders are used for mask layers (i.e. even
 numbered layers 2, 4, 6, etc.).  MRC format also imposes constraints
 on the resolutions that can be used.
 The 'MRC-max-stripe-size' feature may be used with MRC coding, and
 indicates the maximum number of scan lines in each MRC stripe.  The
 legal constraints are:
    (MRC-max-stripe-size<=256)
    (MRC-max-stripe-size>=0)
 These values indicate upper bounds on the stripe size.  The actual
 value may vary between stripes, and the actual size for each stripe
 is indicated in the image data.

4. Examples

 The level of detail captured here reflects that used for capability
 identification in Group 3 facsimile.

4.1 Simple mode Internet fax system

 This example describes the capabilities of a typical simple mode
 Internet fax system.  Note that TIFF profile S is required to be
 supported by such a system.
    (& (image-file-structure=TIFF-minimal)
       (MRC-mode=0)
       (color=Binary)
       (image-coding=MH) (MRC-mode=0)
       (| (& (dpi=204) (dpi-xyratio=[204/98,204/196]) )
          (& (dpi=200) (dpi-xyratio=[200/100,1]) ) )
       (size-x<=2150/254)
       (paper-size=A4)

Klyne & McIntyre Standards Track [Page 13] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

       (ua-media=stationery) )

4.2 High-end black-and-white Internet fax system

 This would include support for B/W JBIG and be equivalent to what is
 sometimes called "Super G3", except that Internet fax functionality
 would be added.
    (& (image-file-structure=TIFF)
       (MRC-mode=0)
       (color=Binary)
       (| (& (dpi=204) (dpi-xyratio=[204/98,204/196]) )
          (& (dpi=200) (dpi-xyratio=[200/100,1]) )
          (& (dpi=300) (dpi-xyratio=1) ) )
       (| (image-coding=[MH,MR,MMR])
          (& (image-coding=JBIG)
             (image-coding-constraint=JBIG-T85)
             (JBIG-stripe-size=128) ) )
       (size-x<=2150/254)
       (paper-size=[letter,A4,B4]) )
       (ua-media=stationery) )

4.3 Grey-scale Internet fax system

 This is the previous example extended to handle grey scale multi-
 level images.  In keeping with Group 3 fax, this example requires
 equal x- and y- resolutions for a multi-level image.
    (& (image-file-structure=TIFF)
       (MRC-mode=0)
       (| (& (color=Binary)
             (| (image-coding=[MH,MR,MMR])
                (& (image-coding=JBIG)
                   (image-coding-constraint=JBIG-T85)
                   (JBIG-stripe-size=128) ) )
             (| (& (dpi=204) (dpi-xyratio=[204/98,204/196]) )
                (& (dpi=200) (dpi-xyratio=[200/100,1]) )
                (& (dpi=300) (dpi-xyratio=1) ) )
          (& (color=Grey)
             (color-levels<=256)
             (color-space-CIELAB)
             (color-illuminant=D50)
             (CIELAB-L-min>=0)
             (CIELAB-L-max<=100)
             (| (& (image-coding=JPEG)
                   (image-coding-constraint=JPEG-T4E) )
                (& (image-coding=JBIG)
                   (image-coding-constraint=JBIG-T43)

Klyne & McIntyre Standards Track [Page 14] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

                   (JBIG-stripe-size=128)
                   (image-interleave=stripe) ) )
             (dpi=[100,200,300]) (dpi-xyratio=1) ) )
       (size-x<=2150/254)
       (paper-size=[letter,A4,B4]) )
       (ua-media=stationery) )

4.4 Full-color Internet fax system (JPEG only)

 This adds 24-bit full-color to the previous example.
    (& (image-file-structure=TIFF)
       (MRC-mode=0)
       (| (& (color=Binary)
             (image-coding=[MH,MR,MMR])
             (| (& (dpi=204) (dpi-xyratio=[204/98,204/196]) )
                (& (dpi=200) (dpi-xyratio=[200/100,1]) )
                (& (dpi=300) (dpi-xyratio=1) ) ) )
          (& (color=grey)
             (image-coding=JPEG)
             (image-coding-constraint=JPEG-T4E)
             (color-levels<=256)
             (color-space=CIELAB)
             (color-illuminant=D50)
             (CIELAB-L-min>=0)
             (CIELAB-L-max<=100)
             (dpi=[100,200,300]) (dpi-xyratio=1) )
          (& (color=full)
             (image-coding=JPEG)
             (image-coding-constraint=JPEG-T4E)
             (color-subsampling=["1:1:1","4:1:1"])
             (color-levels<=16777216)
             (color-space=CIELAB)
             (color-illuminant=D50)
             (CIELAB-L-min>=0)
             (CIELAB-L-max<=100)
             (CIELAB-a-min>=-85)
             (CIELAB-a-max<=85)
             (CIELAB-b-min>=-75)
             (CIELAB-b-max<=125)
             (dpi=[100,200,300]) (dpi-xyratio=1) ) )
       (size-x<=2150/254)
       (paper-size=[letter,A4,B4]) )
       (ua-media=stationery) )

Klyne & McIntyre Standards Track [Page 15] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

4.5 Full-color Internet fax system (JPEG and JBIG)

 This adds limited CMY(K), RGB and 16-bit mapped color using JBIG
 coding to the previous example.
    (& (image-file-structure=TIFF)
       (MRC-mode=0)
       (| (& (color=Binary)
             (| (image-coding=[MH,MR,MMR])
                (& (image-coding=JBIG)
                   (image-coding-constraint=JBIG-T85)
                   (JBIG-stripe-size=128) ) )
             (| (& (dpi=204) (dpi-xyratio=[204/98,204/196]) )
                (& (dpi=200) (dpi-xyratio=[200/100,1]) )
                (& (dpi=300) (dpi-xyratio=1) ) ) )
          (& (color=Limited)
             (image-coding=JBIG)
             (image-coding-constraint=JBIG-T43)
             (JBIG-stripe-size=128)
             (image-interleave=stripe)
             (| (& (color-space=[Device-RGB,Device-CMY])
                   (color-levels<=8) )
                (& (color-space=Device-CMYK)
                   (color-levels<=16) ) )
             (dpi=[100,200,300]) (dpi-xyratio=1) )
          (& (color=Mapped)
             (image-coding=JBIG)
             (image-coding-constraint=JBIG-T43)
             (JBIG-stripe-size=128)
             (image-interleave=stripe)
             (color-levels<=65536)
             (color-space=CIELAB)
             (color-illuminant=D50)
             (CIELAB-L-min>=0)
             (CIELAB-L-max<=100)
             (CIELAB-a-min>=-85)
             (CIELAB-a-max<=85)
             (CIELAB-b-min>=-75)
             (CIELAB-b-max<=125)
             (dpi=[100,200,300]) (dpi-xyratio=1) )
          (& (color=grey)
             (| (& (image-coding=JPEG)
                   (image-coding-constraint=JPEG-T4E) )
                (& (image-coding=JBIG)
                   (image-coding-constraint=JBIG-T43)
                   (JBIG-stripe-size=128)
                   (image-interleave=stripe) ) )
             (color-levels<=256)

Klyne & McIntyre Standards Track [Page 16] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

             (color-space=CIELAB)
             (color-illuminant=D50)
             (CIELAB-L-min>=0)
             (CIELAB-L-max<=100)
             (dpi=[100,200,300]) (dpi-xyratio=1) )
          (& (color=full)
             (| (& (image-coding=JPEG)
                   (image-coding-constraint=JPEG-T4E)
                   (color-subsampling=["1:1:1","4:1:1"]) )
                (& (image-coding=JBIG)
                   (image-coding-constraint=JBIG-T43)
                   (JBIG-stripe-size=128)
                   (image-interleave=stripe) ) )
             (color-levels<=16777216)
             (color-space=CIELAB)
             (color-illuminant=D50)
             (CIELAB-L-min>=0)
             (CIELAB-L-max<=100)
             (CIELAB-a-min>=-85)
             (CIELAB-a-max<=85)
             (CIELAB-b-min>=-75)
             (CIELAB-b-max<=125)
             (dpi=[100,200,300]) (dpi-xyratio=1) ) )
       (size-x<=2150/254)
       (paper-size=[letter,A4,B4]) )
       (ua-media=stationery) )

4.6 Full-color Internet fax system (MRC)

 This adds MRC image structures to the previous example.
    (& (image-file-structure=TIFF-MRC)
       (MRC-mode<=1) (MRC-max-stripe-size>=0)
       (| (& (color=binary)
             (| (image-coding=[MH,MR,MMR])
                (& (image-coding=JBIG)
                   (image-coding-constraint=JBIG-T85)
                   (JBIG-stripe-size=128) ) )
             (| (& (dpi=204) (dpi-xyratio=[204/98,204/196]) )
                (& (dpi=200) (dpi-xyratio=[200/100,1]) )
                (& (dpi=[300,400]) (dpi-xyratio=1) ) ) )
          (& (color=limited)
             (| (& (color-space=[Device-RGB,Device-CMY])
                   (color-levels<=8) ) )
             (| (& (color-space=Device-CMYK)
                   (color-levels<=16) ) )
             (image-coding=JBIG)
             (image-coding-constraint=JBIG-T43)

Klyne & McIntyre Standards Track [Page 17] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

             (JBIG-stripe-size=128)
             (image-interleave=stripe)
             (dpi=[100,200,300,400]) (dpi-xyratio=1) )
          (& (color=mapped)
             (color-levels<=65536)
             (image-coding=JBIG)
             (image-coding-constraint=JBIG-T43)
             (JBIG-stripe-size=128)
             (image-interleave=stripe)
             (color-space=CIELAB)
             (CIELAB-L-min>=0)
             (CIELAB-L-max<=100)
             (CIELAB-a-min>=-85)
             (CIELAB-a-max<=85)
             (CIELAB-b-min>=-75)
             (CIELAB-b-max<=125) ) )
             (color-illuminant=D50)
             (dpi=[100,200,300,400]) (dpi-xyratio=1) )
          (& (color=grey)
             (| (& (image-coding=JPEG)
                   (image-coding-constraint=JPEG-T4E) )
                (& (image-coding=JBIG)
                   (image-coding-constraint=JBIG-T43)
                   (JBIG-stripe-size=128)
                   (image-interleave=stripe) ) )
             (color-space=CIELAB)
             (color-levels<=256)
             (color-illuminant=D50)
             (CIELAB-L-min>=0)
             (CIELAB-L-max<=100)
             (dpi=[100,200,300,400]) (dpi-xyratio=1) )
          (& (color=full)
             (| (& (image-coding=JPEG)
                   (image-coding-constraint=JPEG-T4E)
                   (color-subsampling=["1:1:1","4:1:1"]) )
                (& (image-coding=JBIG)
                   (image-coding-constraint=JBIG-T43)
                   (JBIG-stripe-size=128)
                   (image-interleave=stripe) ) )
             (color-levels<=16777216)
             (color-space=CIELAB)
             (color-illuminant=D50)
             (CIELAB-L-min>=0)
             (CIELAB-L-max<=100)
             (CIELAB-a-min>=-85)
             (CIELAB-a-max<=85)
             (CIELAB-b-min>=-75)
             (CIELAB-b-max<=125)

Klyne & McIntyre Standards Track [Page 18] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

             (dpi=[100,200,300,400]) (dpi-xyratio=1) ) )
       (size-x<=2550/254)
       (Paper-size=[Letter,A4,B4])
       (ua-media=stationery) )

4.7 Sender and receiver feature matching

 This example considers sending a document to an enhanced black-and-
 white fax system with the following receiver capabilities:
    (& (| (& (dpi=200) (dpi-xyatio=200/100) )
          (& (dpi=200) (dpi-xyratio=1) )
          (& (dpi=300) (dpi-xyratio=1) )
          (& (dpi=400) (dpi-xyratio=1) ) )
       (color=Binary)
       (| (& (paper-size=A4) (ua-media=[stationery,transparency]) )
          (& (paper-size=B4) (ua-media=continuous) ) )
       (image-coding=[MH,MR,JBIG]) )
 Turning to the document itself, assume it is available to the sender
 in three possible formats, A4 high resolution, B4 low resolution and
 A4 high resolution color, described by:
    (& (dpi=300) (dpi-xyratio=1)
       (color=Binary)
       (paper-size=A4)
       (image-coding=[MMR,JBIG]) )
    (& (dpi=200) (dpi-xyratio=200/100)
       (color=Binary)
       (paper-size=B4)
       (image-coding=[MH,MR]) )
    (& (dpi=300) (dpi-xyratio=1)
       (color=Mapped) (color-levels<=256)
       (paper-size=A4)
       (image-coding=JPEG) )
 These three image formats can be combined into a composite capability
 statement by a logical-OR operation (to describe format-1 OR format-2
 OR format-3):
    (| (& (dpi=300) (dpi-xyratio=1)
          (color=Binary)
          (paper-size=A4)
          (image-coding=[MMR,JBIG]) )
       (& (dpi=200) (dpi-xyratio=200/100)
          (color=Binary)

Klyne & McIntyre Standards Track [Page 19] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

          (paper-size=B4)
          (image-coding=[MH,MR]) )
       (& (dpi=300) (dpi-xyratio=1)
          (color=Mapped) (color-levels=42)
          (paper-size=A4)
          (image-coding=JPEG) ) )
 This could be simplified, but there is little gain in doing so at
 this point.
 The composite document description can be matched with the receiver
 capability description, according to the rules in [2], to yield the
 result:
    (| (& (dpi=300) (dpi-xyratio=1)
          (color=Binary)
          (paper-size=A4)
          (ua-media=[stationery,transparency])
          (image-coding=JBIG) )
       (& (dpi=200) (dpi-xyratio=200/100)
          (color=Binary)
          (paper-size=B4)
          (ua-media=continuous)
          (image-coding=[MH,MR]) ) )
 Points to note about the feature matching process:
 o  The color document option is eliminated because the receiver
    cannot handle either color (indicated by '(color=Mapped)') or
    JPEG coding (indicated by '(image-coding=JPEG)').
 o  The high resolution version of the document with '(dpi=300)' must
    be send using '(image-coding=JBIG)' because this is the only
    available coding of the image data that the receiver can use for
    high resolution documents.  (The available 300dpi document
    codings here are MMR and JBIG, and the receiver capabilities are
    MH, MR and JBIG.)
 o  The low-resolution version of the document can be sent with
    either MH or MR coding as the receiver can deal with either of
    these for low resolution documents.
 o  The high resolution variant of the document is available only for
    A4, so that is the paper-size used in that case.  Similarly the
    low resolution version is sent for B4 paper.
 o  Even though the sender may not understand the 'ua-media' feature
    tag, and does not mention it, the matching rules preserve the

Klyne & McIntyre Standards Track [Page 20] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

    constraint that the B4 document is rendered with
   '(ua-media=continuous)', and the A4 document may be rendered with
   '(ua-media=[stationery,transparency])'.
 Finally, note that when matching an MRC document description, the
 description of each component sub-image must match the capabilities
 of the intended receiver.

5. IANA Considerations

 Appendix A of this document repeats the descriptions of feature tags
 introduced by RFC 2531 [22], with some small revisions.  These have
 been registered in the "IETF tree", according to the procedure
 described in section 3.1.1 of "Media Feature Tag Registration
 Procedure" [1] (i.e. these feature tags are subject to the "IETF
 Consensus" policies described in RFC 2434 [21]).
 Appendix section A.5 introduces one new feature tag (color-
 illuminant) to be registered according to the same procedure.  An
 ASN.1 identifier should be assigned for this new tag and replaced in
 the body of the registration.

6. Security Considerations

 The points raised below are in addition to the general security
 considerations for extended Internet fax [5], and others discussed in
 [2,8,11,12,13]

6.1 Capability descriptions and mechanisms

 Negotiation mechanisms reveal information about one party to other
 parties.  This may raise privacy concerns, and may allow a malicious
 party to make better guesses about the presence of specific security
 holes.
 Most of these concerns pertain to capability information getting into
 the hands of someone who may abuse it.  This document specifies
 capabilities that help a sender to determine what image
 characteristics can be processed by the recipient, not mechanisms for
 their publication.  Implementers and users should take care that the
 mechanisms employed ensure that capabilities are revealed only to
 appropriate persons, systems and agents.

6.2 Specific threats

 1. Unsolicited bulk mail:  if it is known that a recipient can
    process certain types of images, they may be targeted by bulk
    mailers that want to send such images.

Klyne & McIntyre Standards Track [Page 21] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

7. Acknowledgements

 The authors gratefully acknowledge the contributions of the following
 persons who commented on earlier versions of this memo:  James
 Rafferty, Dan Wing, Robert Buckley, Mr Ryuji Iwazaki.  The following
 contributed ideas upon which some of the features described here have
 been based:  Larry Masinter, Al Gilman, Koen Holtman.

8. References

 [1]  Holtman, K., Mutz, A. and T. Hardie, "Media Feature Tag
      Registration Procedure", RFC 2506, March 1999.
 [2]  Klyne, G., "A syntax for describing media feature sets", RFC
      2533, March 1999.
 [3]  Masinter, L., Holtman, K., Mutz, A. and D. Wing, "Media Features
      for Display, Print, and Fax", RFC 2534, March 1999.
 [4]  McIntyre, L. and G. Klyne, "Internet Fax T.30 Feature Mapping",
      RFC 2880, July 2000.
 [5]  Masinter, L. and D. Wing, RFC 2532, "Extended Facsimile Using
      Internet Mail", RFC 2532, March 1999.
 [6]  "Procedures for document facsimile transmission in the general
      switched telephone network", ITU-T Recommendation T.30 (1999),
      International Telecommunications Union, March 1999
 [7]  McIntyre, L., Buckley, R., Venable, D., Zilles, S., Parsons, G.
      and J. Rafferty, "File format for Internet fax", RFC 2301, March
      1998.
 [8]  Toyoda, K., Ohno, H., Murai, J. and D. Wing, "A Simple Mode of
      Facsimile Using Internet Mail", RFC 2305, March 1998.
 [9]  "Continuous-tone color representation method for facsimile"
      ITU-T Recommendation T.42 (1996) International
      Telecommunications Union (Covers custom illuminant, gamut)
 [10] "Colour and gray-scale image representation using lossless
      coding scheme for facsimile" ITU-T Recommendation T.43 (1997)
      International Telecommunications Union.  (Covers JBIG for
      colour/grey images)
 [12] Klyne, G., "Protocol-independent Content Negotiation Framework",
      RFC 2703, September 1999.

Klyne & McIntyre Standards Track [Page 22] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

 [13] "Standardization of Group 3 facsimile terminals for document
      transmission", ITU-T Recommendation T.4 (1999), International
      Telecommunications Union, (Covers basic fax coding formats: MH,
      MR)
 [14] "Facsimile coding schemes and coding control functions for Group
      4 facsimile apparatus", ITU Recommendation T.6, International
      Telecommunications Union,  (Commonly referred to as the MMR
      standard; covers extended 2-D fax coding format).
 [15] "Mixed Raster Content (MRC)", ITU-T Recommendation T.44,
      International Telecommunications Union.
 [16] "Information technology - Digital compression and coding of
      continuous-tone still image - Requirements and guidelines" ITU-T
      Recommendation T.81 (1992) | ISO/IEC 10918-1:1993 International
      Telecommunications Union, (Commonly referred to as JPEG
      standard)
 [17] "Information technology - Coded representation of picture and
      audio information - Progressive bi-level image compression"
      ITU-T Recommendation T.82 (1993) | ISO/IEC 11544:1993
      International Telecommunications Union (Commonly referred to as
      JBIG1 standard)
 [18] "Application profile for Recommendation T.82 - Progressive bi-
      level image compression (JBIG1 coding scheme for facsimile
      apparatus)", ITU-T Recommendation T.85 (1995),International
      Telecommunications Union, (Covers bi-level JBIG).
 [19] "Colorimeter, 2nd ed.", CIE Publication No. 15.2, 1986. (Defines
      CIELAB color space;  use with fax is further constrained by T.42
      [9].)
 [20] Tag Image File Format, Revision 6.0 Adobe Developers Association
      <ftp://ftp.adobe.com/pub/adobe/devrelations/devtechnotes/pdffiles
      /tiff6.pdf> June 1992
 [21] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
      Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
 [22] Klyne, G. and L. McIntyre, "Content feature schema for Internet
      fax", RFC 2531, March 1999.

Klyne & McIntyre Standards Track [Page 23] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

9. Authors' Addresses

 Graham Klyne
 Content Technologies Ltd.
 1220 Parkview,
 Arlington Business Park
 Theale
 Reading, RG7 4SA
 United Kingdom.
 Phone: +44 118 930 1300
 Fax:   +44 118 930 1301
 EMail: GK@ACM.ORG
 Lloyd McIntyre
 Xerox Corporation
 Mailstop PAHV-121
 3400 Hillview Ave.
 Palo Alto, CA 94304 USA
 Phone: +1-650-813-6762
 Fax:   +1-650-845-2340
 EMail: Lloyd.McIntyre@pahv.xerox.com

Klyne & McIntyre Standards Track [Page 24] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

Appendix A: Feature registrations

A.1 Image size

  1. Media Feature tag name(s):
      size-x
      size-y
  1. ASN.1 identifiers associated with these feature tags:
      size-x:      1.3.6.1.8.1.7
      size-y:      1.3.6.1.8.1.8
  1. Summary of the media features indicated:
      These feature tags indicate the size of a displayed, printed
      or otherwise rendered document image;  they indicate
      horizontal (size-x) and vertical (size-y) dimensions.
      The unit of measure is inches (to be consistent with the
      measure of resolution defined by the feature tag 'dpi').
      Where the actual size is available in millimetres, a
      conversion factor of 10/254 may be applied to yield an exact
      inch-based value.
  1. Values appropriate for use with these feature tags:
      Rational (>0)
  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Print and display applications where different media choices
      will be made depending on the size of the recipient device.
  1. Examples of typical use:
      This example describes the maximum scanned image width and
      height for Group 3 fax: 215x297 mm (8.46x11.69 inches):
      (size-x<=2150/254)
      (size-y<=2970/254)

Klyne & McIntyre Standards Track [Page 25] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Related standards or documents:
      The memo "Media Features for Display, Print, and Fax" [3]
      describes features (pix-x, pix-y) for measuring document size
      in pixels.
      Fax applications should declare physical dimensions using the
      features defined here.
  1. Considerations particular to use in individual applications,

protocols, services, or negotiation mechanisms:

      Where no physical size is known or available, but a pixel size
      is known, a notional size should be declared based upon known
      pixel dimensions and a notional resolution of (say) 100dpi
      For example, to describe a 640x480 pixel display:
         (& (size-x<=640/100) (size-y<=480/100) (dpi=100) )
      The notional 100dpi resolution is used as it represents a
      fairly typical resolution for a pixel-limited display.
      Reducing the rational numbers to canonical form gives the
      following equivalent expression:
         (& (size-x<=32/5) (size-y<=24/5) (dpi=100) )
  1. Interoperability considerations:
      For interoperability with other (non-fax) applications that
      use only pixel-based measurements, pixel dimensions (pix-x,
      pix-y) may be declared in addition to physical measurements.
  1. Related feature tags:
      pix-x                 [3]
      pix-y                 [3]
      dpi                   [3]
      dpi-xyratio           [this document]
  1. Intended usage:
      Common

Klyne & McIntyre Standards Track [Page 26] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Author/Change controller:
      IETF

A.2 Resolution aspect ratio

  1. Media Feature tag name(s):
      dpi-xyratio
  1. ASN.1 identifier associated with this feature tag:
      1.3.6.1.8.1.9
  1. Summary of the media features indicated:
      This feature is used to indicate differential horizontal and
      vertical resolution capability.  In the absence of this
      feature, horizontal and vertical resolutions are presumed to
      be the same.
      When this feature tag is specified, any declared resolution
      (dpi) is presumed to apply to the horizontal axis, and the
      vertical resolution is obtained by dividing that declared
      resolution by the resolution ratio.
      The value of this feature is a pure number, since it
      represents the ratio of two resolution values.
  1. Values appropriate for use with this feature tag:
      Rational (>0)
  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Internet fax, and other print or display applications that
      must handle differential horizontal and vertical resolution
      values.
  1. Examples of typical use:
      The following example describes a fax resolution of 204 dpi
      horizontally by 391 dpi vertically:
      (& (dpi=204) (dpi-xyratio=204/391) )

Klyne & McIntyre Standards Track [Page 27] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Related standards or documents:
      The memo "Media Features for Display, Print, and Fax" [3]
      describes a feature (dpi) for measuring document resolution.
  1. Interoperability considerations:
      When interoperating with an application that does not
      recognize the differential resolution feature, resolution
      matching may be performed on the basis of the horizontal
      resolution only, so aspect ratio information may be lost.
  1. Related feature tags:
      dpi                   [3]
      size-x                [this document]
      size-y                [this document]
  1. Intended usage:
      Internet fax
  1. Author/Change controller:
      IETF

A.3 Color levels

  1. Media Feature tag name(s):
      color-levels
  1. ASN.1 identifier associated with this feature tag:
      1.3.6.1.8.1.10
  1. Summary of the media features indicated:
      This feature tag is used to indicate a number of different
      image data pixel color values.
      When mapped (palletized) color is used, this is generally
      different from the number of different colors that can be
      represented through the color mapping function.
      This feature tag is used in conjunction with a 'color' feature
      having a value other than 'Binary'.

Klyne & McIntyre Standards Track [Page 28] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Values appropriate for use with this feature tag:
      Integer  (>=2)
  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Color image printing or display applications where the data
      resource used may depend upon color handling capabilities of
      the recipient.
  1. Examples of typical use:
      To describe recipient capabilities:
      (& (color=limited) (color-levels<=6) )
      (& (color=grey)    (color-levels<=64) )
      (& (color=mapped)  (color-levels<=240) )
      (& (color=full)    (color-levels<=16777216) )
      To describe capabilities used by a document:
      (& (color=limited) (color-levels=4) )
      (& (color=grey)    (color-levels=48) )
      (& (color=mapped)  (color-levels=100) )
      (& (color=full)    (color-levels=32768) )
  1. Related standards or documents:
      The memo "Media Features for Display, Print, and Fax" [3]
      describes a feature (color) for indicating basic color
      capabilities.
  1. Interoperability considerations:
      The actual number of color values used by a document does not,
      in general, exactly match the number that can be handled by a
      recipient.  To achieve a feature match, at least one must be
      declared as an inequality (i.e. not both as equalities).
      It is recommended that a recipient declares the number of
      color values that it can handle as an inequality (<=), and a
      data resource declares the number of colors that it uses with
      an equality, as shown in the examples above.

Klyne & McIntyre Standards Track [Page 29] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Security considerations:
  1. Privacy concerns, related to exposure of personal information:

Where feature matching is used to select content applicable

         to the physical abilities of a user, unusual values for this
         feature tag might give an indication of a user's restricted
         abilities.
  1. Related feature tags:
      color                 [3]
      color-space           [this document]
  1. Intended usage:
      Internet fax
      Color image scanning/rendering applications
  1. Author/Change controller:
      IETF

A.4 Color space

  1. Media Feature tag name(s):
      color-space
  1. ASN.1 identifier associated with this feature tag:
      1.3.6.1.8.1.11
  1. Summary of the media features indicated:
      This feature indicates a color space.
      A color space value provides two types of information:
      o  the color model used to represent a color value, including
         the number of color components
      o  a mapping between color values and their physical
         realizations
      Device color space values are defined for applications where
      the general color representation used is significant, but
      exact color rendering is left to the device used.  Device
      color spaces defined here have values of the form 'Device-
      xxx'.

Klyne & McIntyre Standards Track [Page 30] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

      Calibrated color space values are provided for use with a
      rendering system that is calibrated with respect to some
      indicated definition, and capable of processing device-
      independent color information accordingly.
  1. Values appropriate for use with this feature tag:
      Token
      Device color      Device-RGB   (device dependent RGB)
      spaces:           Device-CMY   (device dependent CMY)
                        Device-CMYK  (device dependent CMYK)
      Calibrated color  CIELAB       (per T.42 [9])
      space:
                        (may be extended by further registrations)
      'Color-space=CIELAB' indicates the CIE L*a*b* colour space,
      using CIED50 illuminant and its perfectly diffuse reflecting
      white point (per T.42 [9]).
  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Color image printing and display applications where the data
      resource used may depend upon color handling capabilities of
      the recipient.
      Scanning applications where the data transferred may depend
      upon the image generation capabilities of the originator.
  1. Examples of typical use:
      To describe rendering or scanning capabilities:
      (color-space=[Device-RGB,CIELAB])
      To describe capabilities assumed by a document for which
      approximate color reproduction is required:
      (color-space=Device-RGB)
      To describe capabilities assumed by a document for which exact
      color reproduction is required:
      (color-space=CIELAB)

Klyne & McIntyre Standards Track [Page 31] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Related standards or documents:
      CIELAB color space is defined in [19]
      CIELAB use for fax is described in ITU T.42 [9]
  1. Interoperability considerations:
      A color-handling receiver should indicate any appropriate
      device color space capability, in addition to any calibrated
      color spaces that it may support.
      Calibrated color spaces are intended to be used when precise
      color matching is required;  otherwise, if applicable, a
      device color space (color-space=Device-xxx) should be
      indicated.
      Documents for which exact color matching is not important
      should indicate a device color space capability, if
      applicable.
      These principles allow sender/receiver feature matching to be
      achieved when exact color matching is not required.
  1. Security considerations:
  1. Privacy concerns, related to exposure of personal information:

Where feature matching is used to select content applicable

         to the physical abilities of a user, unusual values for this
         feature tag might give an indication of a user's restricted
         abilities.
  1. Denial of service concerns related to consequences of

specifying incorrect values:

         Failure to indicate a generic color space capability for a
         device may lead to failure to match color space for an
         application or document that does not require an exact color
         match.
  1. Related feature tags:
      color                 [3]
  1. Related media types or data formats:
      TIFF-FX               [7]

Klyne & McIntyre Standards Track [Page 32] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Intended usage:
      Internet fax
      Color image scanning/rendering applications
  1. Author/Change controller:
      IETF

A.5 CIELAB color illuminant

  1. Media Feature tag name(s):
      color-illuminant
  1. ASN.1 identifier associated with this feature tag:
      1.3.6.1.8.1.29
  1. Summary of the media features indicated:
      This feature indicates a color illuminant.  This has the
      effect of modifying the color space calibration to reflect the
      use of different sources of illumination.
      A color-illuminant value would normally be used only with a
      calibrated color space.
  1. Values appropriate for use with this feature tag:
      Token
      CIELAB illuminant D50
      values:           D65
                        D75
                        SA
                        SC
                        F2
                        F7
                        F11
      Defined by color  CTnnnn where 'nnnn' is a decimal
      temperature:             representation of the illuminant
                               color temperature in Kelvins.
                    (may be extended by further registrations)

Klyne & McIntyre Standards Track [Page 33] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

      NOTE:  The default color illuminant for Group 3 fax is D50.
  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Color image printing and display applications where the data
      resource used may depend upon detailed color handling
      capabilities of the recipient.
      Scanning applications where the data transferred may depend
      upon the image generation capabilities of the originator.
  1. Examples of typical use:
      To describe rendering or scanning capabilities, or to describe
      capabilities assumed by a document for which exact color
      handling capabilities are required:
      (& (color-space=CIELAB) (color-illuminant=D50) )
  1. Related standards or documents:
      CIELAB color illuminant representations are described in ITU
      T.4 [13], Annex E.6.7.
  1. Interoperability considerations:
      A color-handling receiver that supports a calibrated color
      space should indicate any constraint on the illuminants it can
      handle.
      In the absence of a color-illuminant constraint, a receiver is
      presumed to accept and deal with any specified illuminant
      value.
  1. Related feature tags:
      color                 [3]
      color-space           [this document]
  1. Related media types or data formats:
      TIFF-FX               [7]
  1. Intended usage:
      Internet fax
      Color image scanning/rendering applications

Klyne & McIntyre Standards Track [Page 34] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Author/Change controller:
      IETF

A.6 CIELAB color depth

  1. Media Feature tag name(s):
      CIELAB-L-depth
      CIELAB-a-depth
      CIELAB-b-depth
  1. ASN.1 identifiers associated with these feature tags:
      CIELAB-L-depth:   1.3.6.1.8.1.12
      CIELAB-a-depth:   1.3.6.1.8.1.13
      CIELAB-b-depth:   1.3.6.1.8.1.14
  1. Summary of the media features indicated:
      These feature tags indicate a color depth capability;  i.e.
      the level of detail to which an individual CIELAB color
      component can be specified.  They define the number of
      distinct values possible for each of the color components L*,
      a* and b*.
      Typically, this feature would be used with 'color=mapped', and
      possibly 'color=grey' or 'color=full', to indicate the number
      of distinct colors that can be represented.
         NOTE:  this feature tag describes the number of values that
         can be represented for a color component, and does not
         necessarily indicate the number of distinct values that can
         be rendered or resolved by a system.
  1. Values appropriate for use with these feature tags:
      Integer (>0)
  1. These feature tags are intended primarily for use in the

following applications, protocols, services, or negotiation

    mechanisms:
      Color image printing and display applications where the data
      resource used may depend upon color handling capabilities of
      the recipient.

Klyne & McIntyre Standards Track [Page 35] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

      Scanning applications where the data transferred may depend
      upon the image generation capabilities of the originator.
  1. Examples of typical use:
      To describe rendering or scanning capabilities:
      (& (color=mapped) (color-levels<=240)
         (CIELAB-L-depth<=128)
         (CIELAB-a-depth<=128)
         (CIELAB-b-depth<=128) )
      (& (color=full) (color-levels<=16777216)
         (CIELAB-L-depth<=256)
         (CIELAB-a-depth<=128)
         (CIELAB-b-depth<=128) )
      To describe capabilities assumed by a document:
      (& (color=mapped) (color-levels=200)
         (CIELAB-L-depth=32)
         (CIELAB-a-depth=32)
         (CIELAB-b-depth=32) )
      (& (color=full) (color-levels=32768)
         (CIELAB-L-depth=128)
         (CIELAB-a-depth=32)
         (CIELAB-b-depth=32) )
  1. Related standards or documents:
      The memo "Media Features for Display, Print, and Fax" [3]
      defines a feature (color) for indicating basic color
      capabilities.
      CIELAB color space is defined in [19]
      CIELAB use for fax is described in ITU T.42 [9]
  1. Related feature tags:
      color                 [3]
      color-levels          [this document]
      color-space           [this document]
  1. Intended usage:
      Internet fax
      Color image scanning/rendering applications

Klyne & McIntyre Standards Track [Page 36] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Author/Change controller:
      IETF

A.7 CIELAB color gamut

  1. Media Feature tag name(s):
      CIELAB-L-min
      CIELAB-L-max
      CIELAB-a-min
      CIELAB-a-max
      CIELAB-b-min
      CIELAB-b-max
  1. ASN.1 identifiers associated with these feature tags:
      CIELAB-L-min:     1.3.6.1.8.1.15
      CIELAB-L-max:     1.3.6.1.8.1.16
      CIELAB-a-min:     1.3.6.1.8.1.17
      CIELAB-a-max:     1.3.6.1.8.1.18
      CIELAB-b-min:     1.3.6.1.8.1.19
      CIELAB-b-max:     1.3.6.1.8.1.20
  1. Summary of the media features indicated:
      These feature indicate a supported range of color values, by
      indicating minimum and maximum values used for each color
      component in a CIELAB color space.
      'CIELAB-L-min' and 'CIELAB-L-max' are the minimum and maximum
      values of the L* component.
      'CIELAB-a-min' and 'CIELAB-a-max' are the minimum and maximum
      values of the a* component.
      'CIELAB-b-min' and 'CIELAB-b-max' are the minimum and maximum
      values of the b* component.
         NOTE:  color component values are assumed to be rational
         numbers, so a limited gamut does not necessarily indicate
         limited color resolution.
  1. Values appropriate for use with this feature tag:
      Rational

Klyne & McIntyre Standards Track [Page 37] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Color image printing and display applications where the data
      resource used may depend upon detailed color handling
      capabilities of the recipient.
      Scanning applications where the data transferred may depend
      upon the detailed color image generation capabilities of the
      originator.
  1. Examples of typical use:
      To describe rendering or scanning capabilities:
      (& (CIELAB-L-min>=0)
         (CIELAB-L-max<=100)
         (CIELAB-a-min>=-75)
         (CIELAB-a-max<=+75)
         (CIELAB-b-min>=-85)
         (CIELAB-b-max<=+85) )
      To describe capabilities required by a document:
      (& (CIELAB-L-min=20)
         (CIELAB-L-max=80)
         (CIELAB-a-min=-35)
         (CIELAB-a-max=+55)
         (CIELAB-b-min=-45)
         (CIELAB-b-max=+65) )
  1. Related standards or documents:
      CIELAB color space is defined in [19]
      CIELAB use for fax is described in ITU T.42 [9]
  1. Interoperability considerations:
      When describing a recipient's capabilities, the minimum and
      maximum color component values that can be rendered should be
      indicated by inequalities as shown in the examples above.
      When describing a document, the actual minimum and maximum
      color component values used should be indicated, as shown
      above.

Klyne & McIntyre Standards Track [Page 38] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Security considerations:
  1. Privacy concerns, related to exposure of personal information:

Where feature matching is used to select content applicable

         to the physical abilities of a user, unusual values for this
         feature tag might give an indication of a user's restricted
         abilities.
  1. Related feature tags:
      color                 [3]
      color-space           [this document]
  1. Related media types or data formats:
      TIFF-FX               [7]
  1. Intended usage:
      Internet fax
      Color image scanning/rendering applications
  1. Author/Change controller:
      IETF

A.8 Image file structure

  1. Media Feature tag name(s):
      image-file-structure
  1. ASN.1 identifier associated with this feature tag:
      1.3.6.1.8.1.21
  1. Summary of the media features indicated:
      This feature indicates a file structure used for transfer and
      presentation of image data.
      It does not indicate image data coding:  that is described by
      separate feature tags (image-coding, etc.).

Klyne & McIntyre Standards Track [Page 39] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Values appropriate for use with this feature tag:
      Token
      Image file        TIFF
      structure         TIFF-limited
      options:          TIFF-minimal
                        TIFF-MRC
                        TIFF-MRC-limited
                        (may be extended by further registrations,
                        to cover non-TIFF image file structures)
  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Internet fax, and other print or display applications that
      transfer image data.
  1. Examples of typical use:
      See Appendix B of this memo.
  1. Considerations particular to use in individual applications,

protocols, services, or negotiation mechanisms:

      This tag is intended to provide information about an image
      file structure.  Information about image data coding is
      provided by other tags.
      The following tag values are defined here:
      o  'TIFF' indicates image data enclosed and tagged using TIFF
         structures described in Adobe's definition of TIFF [20].
      o  'TIFF-limited' indicates image data structured using TIFF,
         but with limitations on the placement of Image File
         Descriptors (IFDs) within the file, which are indicated in
         section 4.4.6 of RFC 2301 [7].
      o  'TIFF-minimal' indicates a TIFF image format that meets the
         IFD placement, byte ordering and bit ordering requirements
         of the "minimal black and white mode" described in section
         3.5 of RFC 2301 [7], also known as TIFF-S.

Klyne & McIntyre Standards Track [Page 40] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

      o  'TIFF-MRC' uses a TIFF image structure [20] augmented with a
         sub-IFD structure, described for the "Mixed Raster Content
         mode" in section 8.1.2 of RFC 2301 [7], also known as TIFF-M
         (see also tag 'MRC-mode').
      o  'TIFF-MRC-limited' is the same as 'TIFF-MRC', except that
         the IFD placement is constrained as for 'TIFF-limited'.
      Registration of additional image file structure tags should
      focus similarly on image file structure issues, not raw image
      data compression and coding.  As a guide, an image file
      structure may contain image data coded in a variety of ways,
      and carries information to describe that coding separately
      from MIME content-type labelling, etc.
  1. Related feature tags:
      image-coding          [this document]
      MRC-mode              [this document]
  1. Related media types or data formats:
      TIFF-FX               [7]
      TIFF V6.0 (Adobe)     [20]
  1. Intended usage:
      Internet fax
      Image scanning/rendering applications
  1. Author/Change controller:
      IETF

A.9 Image data coding

  1. Media Feature tag name(s):
      image-coding
  1. ASN.1 identifier associated with this feature tag:
      1.3.6.1.8.1.22
  1. Summary of the media features indicated:
      This feature tag indicates a form of image data compression
      and coding used.

Klyne & McIntyre Standards Track [Page 41] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

      It identifies a generic image coding technique used, without
      regard to any specific profiling of that technique that may be
      applied.  Values for this feature are generally applicable
      across a wide range of image transfer applications.
      This information is distinct from the image file structure and
      MRC information conveyed by the 'image-file-structure' tags.
  1. Values appropriate for use with this feature tag:
      Token             MH
                        MR
                        MMR
                        JBIG
                        JPEG
                        (may be extended by further registrations)
  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Internet fax, and other applications that transfer image data.
  1. Examples of typical use:
      See Appendix B of this memo.
  1. Related standards or documents:
      MH, MR:     ITU T.4 [13]
      MMR:        ITU T.6 [14]
      JPEG:       ITU T.81 [16]
      JBIG:       ITU T.82 [17]
  1. Interoperability considerations:
      To establish the correct conditions for interoperability
      between systems, capabilities to handle the generic image
      coding technique and the specific image coding constraints
      must be established.
  1. Related feature tags:
      image-coding-constraint  [this document]
      JBIG-stripe-size         [this document]
      image-interleave         [this document]

Klyne & McIntyre Standards Track [Page 42] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Related media types or data formats:
      TIFF-FX                  [7]
  1. Intended usage:
      Internet fax
      Image scanning/rendering applications
  1. Author/Change controller:
      IETF

A.10 Image coding constraint

  1. Media Feature tag name(s):
      image-coding-constraint
  1. ASN.1 identifier associated with these feature tags:
      1.3.6.1.8.1.23
  1. Summary of the media features indicated:
      This feature tag qualifies the 'image-coding' feature with a
      specific profile or usage constraints.
      Values for this feature are generally specific to some given
      value of 'image-coding' and also to some restricted
      application or class of applications.
  1. Values appropriate for use with this feature tag:
      Token             JBIG-T85    (bi-level, per ITU T.85)
                        JBIG-T43    (multi-level, per ITU T.43)
                        JPEG-T4E    (per ITU T.4, Annex E)
                        (may be extended by further registrations)
  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Internet fax, and other applications that transfer image data.
      The specific values for this feature indicated above are
      intended for use with Internet fax.

Klyne & McIntyre Standards Track [Page 43] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Examples of typical use:
      See Appendix B of this memo.
  1. Related standards or documents:
      JBIG-T85:   ITU T.85 [18]
      JBIG-T43:   ITU T.43 [10]
      JPEG-T4E:   ITU T.4 Annex E [13]
  1. Interoperability considerations:
      To establish the correct conditions for interoperability
      between systems, capabilities to handle the generic image
      coding technique and the specific image coding constraints
      must be established.
  1. Related feature tags:
      image-coding             [this document]
      JBIG-stripe-size         [this document]
      image-interleave         [this document]
  1. Related media types or data formats:
      TIFF-FX                  [7]
  1. Intended usage:
      Internet fax
      Color image scanning/rendering applications
  1. Author/Change controller:
      IETF

A.11 JBIG stripe size

  1. Media Feature tag name(s):
      JBIG-stripe-size
  1. ASN.1 identifier associated with these feature tags:
      1.3.6.1.8.1.24

Klyne & McIntyre Standards Track [Page 44] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Summary of the media features indicated:
      This feature is a specific usage constraint that is applied to
      JBIG image coding (image-coding=JBIG), and indicates the
      allowable size for each stripe of an image, except the last.
      A stripe of a JBIG image is a delimited horizontal band of
      compressed image data that can be decompressed separately from
      the surrounding data.
  1. Values appropriate for use with this feature tag:
      Integer  (>0)
  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Internet fax, and other applications that transfer image data.
  1. Examples of typical use:
      (JBIG-stripe-size=128)
      (JBIG-stripe-size>0)
  1. Related standards or documents:
      JBIG:       ITU T.82 [17]
      JBIG-T85:   ITU T.85 [18]
      JBIG-T43:   ITU T.43 [10]
  1. Considerations particular to use in individual applications,

protocols, services, or negotiation mechanisms:

      In the case of Internet fax, the specific constraints allowed
      for a receiver are those given as examples above.
      Specifying a stripe size that is not limited (JBIG-stripe-
      size>0) means that an entire page of image data is encoded as
      a single unit.  This may place considerable demands on the
      memory of a receiving system, as the entire stripe needs to be
      buffered in memory.
  1. Interoperability considerations:
      To establish the correct conditions for interoperability
      between systems, capabilities to handle the generic image
      coding technique and the specific image coding constraints
      must be established.

Klyne & McIntyre Standards Track [Page 45] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Related feature tags:
      image-coding             [this document]
      image-coding-constraint  [this document]
      image-interleave         [this document]
  1. Related media types or data formats:
      TIFF-FX                  [7]
  1. Intended usage:
      Internet fax
      Color image scanning/rendering applications
  1. Author/Change controller:
      IETF

A.12 Image interleave

  1. Media Feature tag name(s):
      image-interleave
  1. ASN.1 identifier associated with this feature tag:
      1.3.6.1.8.1.25
  1. Summary of the media features indicated:
      This feature indicates an image interleave capability.
      It may be used with JBIG images (image-coding=JBIG) to
      indicate color plane interleaving of either stripes or entire
      image planes.
  1. Values appropriate for use with this feature tag:
      Token             Stripe
                        Plane
  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Internet fax, and other applications that transfer image data.

Klyne & McIntyre Standards Track [Page 46] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Examples of typical use:
      (image-interleave=stripe)
      (image-interleave=[stripe,plane])
  1. Considerations particular to use in individual applications,

protocols, services, or negotiation mechanisms:

      Specifying a plane interleave means that an entire page of
      image data must be buffered in order to generate or render the
      image.  This may place considerable demands on the memory of a
      sending or receiving system.
  1. Related feature tags:
      image-coding             [this document]
      JBIG-stripe-size         [this document]
  1. Related media types or data formats:
      TIFF-FX                  [7]
  1. Intended usage:
      Internet fax
      Color image scanning/rendering applications
  1. Author/Change controller:
      IETF

A.13 Color subsampling

  1. Media Feature tag name(s):
      color-subsampling
  1. ASN.1 identifier associated with this feature tag:
      1.3.6.1.8.1.26
  1. Summary of the media features indicated:
      This feature tag indicates whether color information may be
      subsampled with respect to luminance data.

Klyne & McIntyre Standards Track [Page 47] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

      It is used with continuous color images (color=full), color
      spaces that use separate luminance and color components
      (e.g. color-space=LAB), and image file structures that support
      color subsampling.
  1. Values appropriate for use with this feature tag:
      String            "1:1:1"
                        This value indicates a full set of color
                        component samples for each luminance
                        component sample.
                        "4:1:1"
                        This value indicates one set of color component
                        samples for each 4 luminance samples.
                        (may be extended by further registrations)
  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Color image printing and display applications where the data
      resource used may depend upon color handling capabilities of
      the recipient.
      Scanning applications where the data transferred may depend
      upon the image generation capabilities of the originator.
  1. Examples of typical use:
      (& (color=full) (color-space=[LAB,CIELAB])
         (color-subsampling=["1:1:1","4:1:1"]) )
  1. Related feature tags:
      color                 [3]
      color-space           [this document]
      image-file-structure  [this document]
  1. Related media types or data formats:
      TIFF-FX               [7]
  1. Intended usage:
      Internet fax
      Color image scanning/rendering applications

Klyne & McIntyre Standards Track [Page 48] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Author/Change controller:
      IETF

A.14 MRC availability and mode

  1. Media Feature tag name(s):
      MRC-mode
  1. ASN.1 identifier associated with this feature tag:
      1.3.6.1.8.1.27
  1. Summary of the media features indicated:
      This feature is used to indicate the availability of MRC
      (mixed raster content) image format capability, and also the
      MRC mode available.  A zero value indicates MRC is not
      available, a non-zero value (in the range 1..7) indicates the
      available MRC mode number.
      An MRC formatted document is actually a collection of several
      images, each of which is described by a separate feature
      collection.  An MRC-capable receiver is presumed to be capable
      of accepting any combination of contained images that conform
      to the MRC construction rules, where each such image matches
      the separately declared resolution, color capability, color
      model, image coding, and any other capabilities.
         NOTE: an MRC formatted document may appear within a
         TIFF image file structure.
         Within an MRC-formatted document, multi-level coders
         are used for foreground and background images (i.e.
         odd-numbered layers: 1, 3, 5, etc.) and bi-level coders
         are used for mask layers (i.e. even numbered layers 2,
         4, 6, etc.).
  1. Values appropriate for use with this feature tag:
      Integer (0..7)

Klyne & McIntyre Standards Track [Page 49] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Internet fax, and other applications that transfer image data.
  1. Examples of typical use:
      See Appendix B of this document.
  1. Related standards or documents:
      ITU T.44 [15]
  1. Interoperability considerations:
      To establish the correct conditions for interoperability
      between systems, capabilities to handle the MRC mode and any
      contained image coding techniques must be established.
  1. Related feature tags:
      image-coding             [this document]
      MRC-max-stripe-size      [this document]
  1. Related media types or data formats:
      TIFF-FX                  [7]
  1. Intended usage:
      Internet fax
      Color image scanning/rendering applications
  1. Author/Change controller:
      IETF

A.15 MRC maximum stripe size

  1. Media Feature tag name(s):
      MRC-max-stripe-size
  1. ASN.1 identifier associated with this feature tag:
      1.3.6.1.8.1.28

Klyne & McIntyre Standards Track [Page 50] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

  1. Summary of the media features indicated:
      This feature may be used with MRC coding (MRC-mode>=1), and
      indicates the maximum number of scan lines in each MRC stripe.
      The value given indicates an upper bound on the stripe size.
      The actual value may vary between stripes, and the actual size
      for each stripe is indicated in the image data.
  1. Values appropriate for use with this feature tag:
      Integer (>0)
  1. The feature tag is intended primarily for use in the following

applications, protocols, services, or negotiation mechanisms:

      Internet fax, and other applications that transfer image data.
  1. Examples of typical use:
      (MRC-max-stripe-size<=256)
      (MRC-max-stripe-size>=0)
  1. Considerations particular to use in individual applications,

protocols, services, or negotiation mechanisms:

      For Internet fax, the legal constraints for an image receiver
      are those given as examples above.
  1. Related feature tags:
      MRC-mode              [this document]
  1. Related media types or data formats:
      TIFF-FX               [7]
  1. Intended usage:
      Internet fax
      Color image scanning/rendering applications
  1. Author/Change controller:
      IETF

Klyne & McIntyre Standards Track [Page 51] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

Appendix B: TIFF mode descriptions

 This appendix contains descriptions of the TIFF modes defined by
 RFC 2301 [7], presented as feature set expressions in the form
 defined by "A syntax for describing media feature sets" [2] and
 using the feature schema introduced by this document.
 These may be taken as illustrations of the feature set combinations
 that are required for the corresponding TIFF profiles described by
 RFC 2301.
 TIFF-S has no optional elements, so is presented as a single
 feature set.  Other profiles are presented as (TIFF-x-base) and
 (TIFF-x-full) indicating the minimum and full feature sets
 associated with each profile.
    (TIFF-S) :-
         (& (image-file-structure=TIFF-S)
            (color=Binary)
            (image-coding=MH) (MRC-mode=0)
            (| (& (dpi=200)
                  (dpi-xyratio=[200/100,200/200])
                  (size-x=1728/200) )
               (& (dpi=204)
                  (dpi-xyratio=[204/98,204/196]
                  (size-x=1728/204) ) )
            (paper-size=A4) )
    (TIFF-F-base) :-
       (& (image-file-structure=TIFF-F)
          (color=Binary)
          (image-coding=MH) (MRC-mode=0)
          (dpi=204)
          (dpi-xyratio=[204/98,204/196])
          (size-x=1728/204)
          (paper-size=A4) )
    (TIFF-F-full) :-
       (& (image-file-structure=TIFF-F)
          (color=Binary)
          (image-coding=[MH,MR,MMR]) (MRC-mode=0)
          (| (& (dpi=200)
                (dpi-xyratio=[200/100,200/200])
                (size-x=[1728/200,2048/200,2432/200]) )
             (& (dpi=204)
                (dpi-xyratio=[204/98,204/196,204/391])
                (size-x=[1728/204,2048/204,2432/204]) )
             (& (dpi=300)

Klyne & McIntyre Standards Track [Page 52] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

                (dpi-xyratio=300/300)
                (size-x=[2592/300,3072/300,3648/300]) )
             (& (dpi=400)
                (dpi-xyratio=400/400)
                (size-x=[3456/400,4096/400,4864/400]) )
             (& (dpi=408)
                (dpi-xyratio=408/391)
                (size-x=[3456/408,4096/408,4864/408]) ) )
           (paper-size=[A4, B4, A3, letter, legal]) )
    (TIFF-J-base) :-
       (& (image-file-structure=TIFF-J)
          (color=Binary)
          (MRC-mode=0)
          (image-coding=JBIG)
          (image-coding-constraint=JBIG-T85)
          (JBIG-stripe-size=128)
          (dpi=204)
          (dpi-xyratio=[204/98,204/196])
          (size-x=1728/204)
          (paper-size=A4) )
    (TIFF-J-full) :-
       (& (image-file-structure=TIFF-J)
          (color=Binary)
          (MRC-mode=0)
          (image-coding=JBIG)
          (image-coding-constraint=JBIG-T85)
          (JBIG-stripe-size>0)
          (| (& (dpi=200)
                (dpi-xyratio=[200/100,200/200])
                (size-x=[1728/200,2048/200,2432/200]) )
             (& (dpi=204)
                (dpi-xyratio=[204/98,204/196,204/391])
                (size-x=[1728/204,2048/204,2432/204]) )
             (& (dpi=300)
                (dpi-xyratio=300/300)
                (size-x=[2592/300,3072/300,3648/300]) )
             (& (dpi=400)
                (dpi-xyratio=400/400)
                (size-x=[3456/400,4096/400,4864/400]) )
             (& (dpi=408)
                (dpi-xyratio=408/391)
                (size-x=[3456/408,4096/408,4864/408]) ) )
          (paper-size=[A4, B4, A3, letter, legal]) )
    (TIFF-C-base) :-
       (& (image-file-structure=TIFF-C)

Klyne & McIntyre Standards Track [Page 53] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

          (color=grey)
          (color-levels<=256)
          (MRC-mode=0)
          (image-coding=JPEG) (image-coding-constraint=JPEG-T4E)
          (color-space=CIELAB)
          (CIELAB-L-depth<=101)
          (CIELAB-L-min>=0)
          (CIELAB-L-max<=100)
          (color-illuminant=D50)
          (dpi=200) (dpi-xyratio=1)
          (size-x=864/100)
          (paper-size=A4) )
    (TIFF-C-full) :-
       (& (image-file-structure=TIFF-C)
          (image-coding=JPEG) (image-coding-constraint=JPEG-T4E)
          (color-space=CIELAB)
          (| (& (color=grey)
                (color-levels<=4096)
                (CIELAB-L-depth<=4096) )
             (& (color=full)
                (color-levels<=68719476736)
                (color-subsampling=["4:1:1","1:1:1"])
                (CIELAB-L-depth<=4096)
                (CIELAB-a-depth<=4096)
                (CIELAB-b-depth<=4096) ) )
          (MRC-mode=0)
          (dpi=[100,200,300,400]) (dpi-xyratio=1)
          (size-x=[864/100,1024/100,1216/100])
          (paper-size=[A4, B4, A3, letter, legal]) )
    (TIFF-L-base) :-
       (& (image-file-structure=TIFF-L)
          (MRC-mode=0)
          (image-coding=JBIG)
          (image-coding-constraint=JBIG-T43)
          (JBIG-stripe-size=128)
          (image-interleave=stripe)
          (color=grey)
          (color-levels<=256)
          (color-space=CIELAB)
          (CIELAB-L-depth=101)
          (CIELAB-L-min>=0)
          (CIELAB-L-max<=100)
          (color-illuminant=D50)
          (dpi=200) (dpi-xyratio=1)
          (size-x=864/100)
          (paper-size=A4) )

Klyne & McIntyre Standards Track [Page 54] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

    (TIFF-L-full) :-
       (& (image-file-structure=TIFF-L)
          (MRC-mode=0)
          (image-coding=JBIG)
          (image-coding-constraint=JBIG-T43)
          (JBIG-stripe-size>0)
          (image-interleave=[stripe, plane])
          (| (& (color=limited)
                (color-levels<=8)
                (color-space=[Device-RGB, Device-CMY] ) )
             (& (color=limited)
                (color-levels<=16)
                (color-space=Device-CMYK) )
             (& (color=mapped)
                (color-levels<=65536)
                (color-space=CIELAB)
                (CIELAB-L-depth<=4096)
                (CIELAB-a-depth<=4096)
                (CIELAB-b-depth<=4096) )
             (& (color=grey)
                (color-levels<=4096)
                (color-space=CIELAB)
                (CIELAB-L-depth<=4096) )
             (& (color=full)
                (color-space=CIELAB)
                (color-levels<=68719476736)
                (CIELAB-L-depth<=4096)
                (CIELAB-a-depth<=4096)
                (CIELAB-b-depth<=4096)
                (CIELAB-L-min>=0) ) )
          (dpi=[100,200,300,400]) (dpi-xyratio=1)
          (size-x=[864/100,1024/100,1216/100])
          (paper-size=[A4, B4, A3, letter, legal]) )
    (TIFF-M-base) :-
       (& (image-file-structure=TIFF-M)
          (MRC-mode>=1)
          (MRC-max-stripe-size<=256) )
    (TIFF-M-full) :-
       (& (image-file-structure=TIFF-M)
          (MRC-mode>=1) )

Klyne & McIntyre Standards Track [Page 55] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

 Support for multiple TIFF profiles may be indicated by combining
 their expressions with the OR operator; e.g.
    (| (TIFF-F) (TIFF-S) (TIFF-J) )
 indicates support for all black-and-white modes.
 TIFF-M is a composite mode and must be used in conjunction with
 some other mode to define the particular capabilities of a
 receiver; e.g.
    (| (TIFF-M-base)
       (TIFF-S) (TIFF-J-full) (TIFF-C-base) (TIFF-L-full) )
 Each sub-image in an MRC image must conform to the capabilities
 indicated AND also to any additional constraints imposed by the MRC
 structure, such as bi-level mask layer, etc.  See sections A.13 and
 section 3.7.

Klyne & McIntyre Standards Track [Page 56] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

Appendix C: Changes from RFC 2531

 00a  23-Jun-1999  Updated Appendix B with more complete TIFF-FX
                   profile descriptions.  Added note to section 3.5
                   clarifying the meaning of (color=limited) in the
                   context of Internet fax.  Added note to section
                   3.6 and A.6 to clarify interpretation of color
                   depth.  In A.6, noted that color gamut is not the
                   same as color resolution;  fixed example.  Split
                   section 3.7 into two sections, dealing with simple
                   image coding options and MRC composite image
                   options.  Added new feature tag 'color-illuminant'
                   (sections 3.6, A.5).  Added cross-references from
                   TIFF-M image file structure to MRC-mode tag.
                   Updated introduction and references.
 00b  10-Aug-1999  Bring examples into line with T.30 mapping
                   document [4], and reorganize to make the
                   expression structure less complex.  Add details of
                   mailing list for discussion.  Added JPEG-only
                   colour example.  Change definition of image-file-
                   structure tag to indicate more precisely what is
                   being defined, and to draw out the distinction
                   between a file structure to contain MRC images
                   (image-file-structure), and the MRC image model
                   (MRC-mode).
 01a  01-Oct-1999  Update author's address and some references.
 01b  05-Jan-2000  Incorporate last-call review comments (all
                   editorial).

Klyne & McIntyre Standards Track [Page 57] RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000

Full Copyright Statement

 Copyright (C) The Internet Society (2000).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Klyne & McIntyre Standards Track [Page 58]

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