One document matched: draft-ietf-fax-feature-schema-04.txt
Differences from draft-ietf-fax-feature-schema-03.txt
IETF Fax working group Graham Klyne
INTERNET-DRAFT 5GM/Content Technologies
Category: Work-in-progress Lloyd McIntyre
Xerox Corporation
14 December 1998
Expires: June 1999
Content feature schema for Internet fax
<draft-ietf-fax-feature-schema-04.txt>
Status of this memo
[[INTENDED STATUS: 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.]]
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Copyright Notice
Copyright (C) The Internet Society 1998. All Rights Reserved.
Abstract
This document defines a content feature schema that is a profile of
the media feature registration mechanisms [1,2,3] for use in
performing capability identification between extended Internet fax
systems [5].
This document does not describe any specific mechanisms for
communicating capability information, but does presume that any
such mechanisms will transfer textual values. It specifies a
textual format to be used for describing Internet fax capability
information.
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Table of contents
1. Introduction ............................................3
1.1 Organization of this document 3
1.2 Terminology and document conventions 3
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 10
4. Examples ................................................12
4.1 Simple mode Internet fax system 12
4.2 High-end black-and-white Internet fax system 12
4.3 Grey-scale Internet fax system 13
4.4 Full-color Internet fax system (JPEG) 14
4.5 Full-color Internet fax system (MRC) 15
4.6 Sender and receiver feature matching 15
5. Security considerations .................................18
5.1 Capability descriptions and mechanisms 18
5.2 Specific threats 18
6. Full copyright statement ................................18
7. Acknowledgements ........................................19
8. References ..............................................19
9. Authors' addresses ......................................22
Appendix A: Feature registrations ..........................23
A.1 Image size 23
A.2 Resolution aspect ratio 25
A.3 Color levels 27
A.4 Color space 29
A.5 CIELAB color depth 32
A.6 CIELAB color gamut 34
A.7 Image file structure 37
A.8 Image data coding 39
A.9 Image coding constraint 41
A.10 JBIG stripe size 43
A.11 Image interleave 45
A.12 Color subsampling 47
A.13 MRC availability and mode 49
A.14 MRC maximum stripe size 51
Appendix B: TIFF mode descriptions .........................53
Appendix C: Revision history ...............................54
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1. Introduction
This document defines a content feature schema that is a profile of
the media feature registration mechanisms [1,2,3] for use in
performing capability identification between extended Internet fax
systems [5].
This document does not describe any specific mechanisms for
communicating capability information, but does presume that any
such mechanisms will transfer textual values. It specifies a
textual format to be used for describing Internet fax capability
information.
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 "eifax 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.
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"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.
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 eifax 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 (eifax)
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 eifax system is
expected to recognize its ability or non-ability to handle.
Definitive descriptions of feature tags are indicated by reference
to their registration per the media feature registration procedure
[1] (some of which are appended to this document)
NOTE: The presence of a feature tag in this list does
not mean that an eifax 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 eifax system is not prevented from
recognizing and offering additional feature tags. The
list below is intended to provide a basic vocabulary that
all eifax systems can use in a consistent fashion.
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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'.
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.
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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].
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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. No ability to indicate
any specific or named color is implied by this option.
NOTE: Some devices might use different intensity levels
rather than different hues for distinction.
'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.
For 'Mapped', 'Grey' and 'Full' color, additional feature tags
(section 3.6) may be used to further qualify the color
reproduction.
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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)
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
- "raw bit stream" is a stream of coded bits
(A) indicates image coding/decoding (MH,MR,MMR,JPEG,JBIG,etc.)
- "pixel values" are a single numeric value per picture element
that designates the color of that element.
(B) indicates pixel-to-color value mapping
- "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).
- "physical rendition" is a color value physically realized on a
display, printer or other device.
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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 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.
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.
'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 palettized color, or with full color where each
color component has a different number of possible values.
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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.
3.7 Image coding
Feature tag name Legal values
---------------- ------------
image-file- TIFF-S
structure TIFF-F
TIFF-J
TIFF-C
TIFF-L
TIFF-M
(may be extended by further registrations,
to cover non-TIFF image file structures)
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)
MRC-mode <Integer> (0..7) (per ITU T.44 [15])
MRC-max-stripe-size <Integer>
Reference: this document, appendix A.
'image-file-structure' defines how the coded image data is wrapped
and formatted. Options defined here are the various profiles of
TIFF-FX, per RFC 2301 [7]. These options apply to overall
formatting of the image data (TIFF file format, byte ordering, bit
ordering, etc.) and do not define specific image coding issues that
are covered by other aspects of the TIFF-FX profile specifications.
'image-coding' describes how the 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.
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'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.
The 'MRC-mode' 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 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 and declared image-coding capabilities.
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.).
NOTE: an MRC formatted document may appear within a TIFF
image file structure, so this separate feature is needed
to capture the full range of possible capabilities.
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-stripe-size=[0..256])
(MRC-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.
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4. Examples
Some of the examples contain comments introduced by '--...'. These
are not part of the allowed capability description syntax. They
are included here to explain some of the constructs used.
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 application S is required to
be supported by such a system.
(& (color=Binary)
(image-file-structure=TIFF-S)
(dpi=200)
(dpi-xyratio=[200/100,200/200])
(paper-size=A4)
(image-coding=MH) (MRC-mode=0)
(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.
(& (color=Binary)
(image-file-structure=[TIFF-S,TIFF-F,TIFF-J])
(| (& (dpi=200) (dpi-xyratio=200/100) ) -- 200*100
(& (dpi=200) (dpi-xyratio=1) ) -- 200*200
(& (dpi=204) (dpi-xyratio=204/391) ) -- 204*391
(& (dpi=300) (dpi-xyratio=1) ) ) -- 300*300
(| (image-coding=[MH,MR,MMR])
(& (image-coding=JBIG)
(image-coding-constraint=JBIG-T85)
(JBIG-stripe-size=128) ) )
(MRC-mode=0)
(paper-size=[A4,B4]) )
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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.
(& (| (& (color=Binary)
(image-file-structure=[TIFF-S,TIFF-F,TIFF-J])
(| (image-coding=[MH,MR,MMR])
(& (image-coding=JBIG)
(image-coding-constraint=JBIG-T85)
(JBIG-stripe-size=128) ) )
(| (& (dpi=200) (dpi-xyratio=200/100) )
(& (dpi=200) (dpi-xyratio=1) )
(& (dpi=204) (dpi-xyratio=204/391) )
(& (dpi=300) (dpi-xyratio=1) ) ) )
(& (color=Grey)
(image-file-structure=[TIFF-C,TIFF-L])
(color-levels<=256)
(color-space-CIELAB)
(| (& (image-coding=JPEG)
(image-coding-constraint=JPEG-T4E) )
(& (image-coding=JBIG)
(image-coding-constraint=JBIG-T43)
(JBIG-stripe-size=128)
(image-interleave=stripe) ) )
(dpi=[100,200,300])
(dpi-xyratio=1) ) )
(MRC-mode=0)
(paper-size=[A4,B4]) )
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4.4 Full-color Internet fax system (JPEG)
This adds 16-bit full-color to the previous example.
(& (| (& (color=Binary)
(image-file-structure=[TIFF-S,TIFF-F,TIFF-J])
(| (image-coding=[MH,MR,MMR])
(& (image-coding=JBIG)
(image-coding-constraint=JBIG-T85)
(JBIG-stripe-size=128) ) )
(| (& (dpi=200) (dpi-xyratio=200/100) )
(& (dpi=200) (dpi-xyratio=1) )
(& (dpi=204) (dpi-xyratio=204/391) )
(& (dpi=300) (dpi-xyratio=1) ) ) )
(& (| (& (color=Grey) (color-levels<=256) )
(& (color=Full) (color-levels<=65536)
(color-subsampling=["1:1:1","4:1:1"]) ) )
(image-file-structure=[TIFF-C,TIFF-L])
(color-space=CIELAB)
(| (& (image-coding=JPEG)
(image-coding-constraint=JPEG-T4E) )
(& (image-coding=JBIG)
(image-coding-constraint=JBIG-T43)
(JBIG-stripe-size=128)
(image-interleave=stripe) ) )
(dpi=[100,200,300])
(dpi-xyratio=1) ) )
(MRC-mode=0)
(paper-size=[A4,B4]) )
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4.5 Full-color Internet fax system (MRC)
(& (| (& (color=Binary)
(image-file-structure=[TIFF-S,TIFF-F,TIFF-J])
(MRC-mode=0)
(image-coding=[MH,MMR])
(| (& (dpi=200) (dpi-xyratio=[200/100,1]) )
(& (dpi=204) (dpi-xyratio=204/391) )
(& (dpi=300) (dpi-xyratio=1) )
(& (dpi=400) (dpi-xyratio=1) ) ) )
(& (image-file-structure=[TIFF-C,TIFF-L])
(| (& (color=Grey) (color-levels<=256) )
(& (color=Full) (color-levels<=65536)
(color-subsampling=["1:1:1","4:1:1"]) ) )
(color-space=CIELAB)
(MRC-mode=0)
(image-coding=JPEG)
(image-coding-constraint=JPEG-T4E)
(dpi=[100,200,300,400])
(dpi-xyratio=1) )
(& (image-file-structure=TIFF-M)
(MRC-mode=1) (MRC-stripe-size=[0..256])
(image-coding=[MH,MMR,JPEG])
(| (color=Binary)
(& (color=Grey) (color-levels<=256) )
(& (color=Full) (color-levels<=65536)
(color-subsampling=["1:1:1","4:1:1"]) ) )
(color-space=CIELAB)
(dpi=[100,200,300,400])
(dpi-xyratio=1) ) )
(paper-size=[A4,B4]) )
4.6 Sender and receiver feature matching
This example considers sending a document to a high-end black-and-
white fax system with the following receiver capabilities:
(& (| (& (dpi=200) (dpi-xyratio=200/100) ) -- 200*100
(& (dpi=200) (dpi-xyratio=1) ) -- 200*200
(& (dpi=300) (dpi-xyratio=1) ) -- 300*300
(& (dpi=400) (dpi-xyratio=1) ) ) -- 400*400
(color=Binary)
(| (& (paper-size=A4) (ua-media=[stationery,transparency]) )
(& (paper-size=B4) (ua-media=continuous) ) )
(image-coding=[MH,MR,JBIG]) )
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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)
(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.
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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
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.
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5. 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]
5.1 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. Implementors and users should take care
that the mechanisms employed ensure that capabilities are revealed
only to appropriate persons, systems and agents.
5.2 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.
6. Full copyright statement
Copyright (C) The Internet Society 1998. 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.
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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.
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. The following
contributed ideas upon which some of the features described here
have been based: Larry Masinter, Al Gilman, Koen Holtman.
8. References
[1] "Media Feature Tag Registration Procedure"
Koen Holtman, TUE
Andrew Mutz, Hewlett-Packard
Ted Hardie, NASA
Internet draft: <draft-ietf-conneg-feature-reg-03.txt>
Work in progress, July 1998.
[2] "A syntax for describing media feature sets"
Graham Klyne, 5GM/Content Technologies
Internet draft: <draft-ietf-conneg-feature-syntax-00.txt>"
Work in progress, September 1998.
[3] "Media Features for Display, Print, and Fax"
Larry Masinter, Xerox PARC
Koen Holtman, TUE
Andrew Mutz, Hewlett-Packard
Dan Wing, Cisco Systems
Internet draft: <draft-ietf-conneg-media-features-02.txt>
Work in progress, September 1998.
[4] "Internet fax feature mapping from Group 3 fax"
Lloyd McIntyre, Xerox Corporation
Graham Klyne, 5GM/Content Technologies
Internet draft: <draft-ietf-fax-feature-T30-mapping-00.txt>
Work in progress, August 1998.
[5] "Extended Facsimile Using Internet Mail
Larry Masinter, Xerox Corporation
Dan Wing, Cisco Systems
Internet draft: <draft-ietf-fax-eifax-04.txt>
Work in progress, September 1998.
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[6] "Procedures for document facsimile transmission in the general
switched telephone network"
ITU-T Recommendation T.30 (1996)
International Telecommunications Union
July 1996
[7] RFC 2301, "File format for Internet fax"
L. McIntyre,
R. Buckley,
D. Venable, Xerox Corporation
S. Zilles, Adobe Systems, Inc.
G. Parsons, Northern Telecom
J. Rafferty, Human Communications
March 1998.
[8] RFC 2305, "A Simple Mode of Facsimile Using Internet Mail"
K. Toyoda
H. Ohno
J. Murai, WIDE Project
D. Wing, Cisco Systems
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)
[11] "Scenarios for the Delivery of Negotiated Content"
T. Hardie, NASA Network Information Center
Internet draft: <draft-ietf-http-negotiate-scenario-02.txt>
Work in progress, November 1997.
[12] "Requirements for protocol-independent content negotiation"
G. Klyne, Integralis Ltd.
Internet draft: <draft-ietf-conneg-requirements-00.txt>
Work in progress, March 1998.
[13] "Standardization of Group 3 facsimile terminals for document
transmission"
ITU-T Recommendation T.4 (1996)
International Telecommunications Union
(Covers basic fax coding formats: MH, MR)
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[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
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9. Authors' addresses
Graham Klyne
5th Generation Messaging Ltd. Content Technologies Ltd.
5 Watlington Street Forum 1, Station Road
Nettlebed Theale
Henley-on-Thames, RG9 5AB Reading, RG7 4RA
United Kingdom United Kingdom.
Telephone: +44 1491 641 641 +44 118 930 1300
Facsimile: +44 1491 641 611 +44 118 930 1301
E-mail: GK@ACM.ORG
Lloyd McIntyre
Xerox Corporation
Mailstop PAHV-121
3400 Hillview Ave.
Palo Alto, CA 94304 USA
Telephone: +1-650-813-6762
Facsimile: +1-650-845-2340
E-mail: Lloyd.McIntyre@pahv.xerox.com
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Appendix A: Feature registrations
A.1 Image size
- Media Feature tag name(s):
size-x
size-y
- ASN.1 identifiers associated with these feature tags:
[[[New assignments by IANA]]]
- 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.
- Values appropriate for use with these feature tags:
Rational (>0)
- 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.
- 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)
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- 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.
- 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) )
- 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.
- Related feature tags:
pix-x [3]
pix-y [3]
dpi [3]
dpi-xyratio [this document]
- Intended usage:
Common
- Author/Change controller:
IETF (Fax Working Group)
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A.2 Resolution aspect ratio
- Media Feature tag name(s):
dpi-xyratio
- ASN.1 identifier associated with this feature tag:
[[[New assignments by IANA]]]
- 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.
- Values appropriate for use with this feature tag:
Rational (>0)
- 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.
- 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) )
- Related standards or documents:
The memo "Media Features for Display, Print, and Fax" [3]
describes a feature (dpi) for measuring document resolution.
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- 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.
- Related feature tags:
dpi [3]
size-x [this document]
size-y [this document]
- Intended usage:
Internet fax
- Author/Change controller:
IETF (Fax Working Group)
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A.3 Color levels
- Media Feature tag name(s):
color-levels
- ASN.1 identifier associated with this feature tag:
[[[New assignments by IANA]]]
- Summary of the media features indicated:
This feature tag is used to indicate a number of different
image data pixel color values.
When mapped (palettized) 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'.
- Values appropriate for use with this feature tag:
Integer (>=2)
- 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.
- 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) )
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- Related standards or documents:
The memo "Media Features for Display, Print, and Fax" [3]
describes a feature (color) for indicating basic color
capabilities.
- 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.
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.
- Security considerations:
- 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.
- Related feature tags:
color [3]
color-space [this document]
- Intended usage:
Internet fax
Color image scanning/rendering applications
- Author/Change controller:
IETF (Fax Working Group)
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A.4 Color space
- Media Feature tag name(s):
color-space
- ASN.1 identifier associated with this feature tag:
[[[New assignments by IANA]]]
- 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'.
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.
- 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]).
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- 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.
- 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)
- Related standards or documents:
CIELAB color space is defined in [19]
CIELAB use for fax is described in ITU T.42 [9]
- Interoperability considerations:
A color-handling receiver should indicate at 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.
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- Security considerations:
- 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.
- 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.
- Related feature tags:
color [3]
- Related media types or data formats:
TIFF-FX [7]
- Intended usage:
Internet fax
Color image scanning/rendering applications
- Author/Change controller:
IETF (Fax Working Group)
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A.5 CIELAB color depth
- Media Feature tag name(s):
CIELAB-L-depth
CIELAB-A-depth
CIELAB-B-depth
- ASN.1 identifiers associated with these feature tags:
[[[New assignments by IANA]]]
- 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 realized.
- Values appropriate for use with these feature tags:
Integer (>0)
- 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.
Scanning applications where the data transferred may depend
upon the image generation capabilities of the originator.
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- 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) )
- 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]
- Related feature tags:
color [3]
color-levels [this document]
color-space [this document]
- Intended usage:
Internet fax
Color image scanning/rendering applications
- Author/Change controller:
IETF (Fax Working Group)
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A.6 CIELAB color gamut
- Media Feature tag name(s):
CIELAB-L-min
CIELAB-L-max
CIELAB-a-min
CIELAB-a-max
CIELAB-b-min
CIELAB-b-max
- ASN.1 identifiers associated with these feature tags:
[[[New assignments by IANA]]]
- 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.
- Values appropriate for use with this feature tag:
Rational
- 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.
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- 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-L-min=-35)
(CIELAB-L-max=+55)
(CIELAB-L-min=-45)
(CIELAB-L-max=+65) )
- Related standards or documents:
CIELAB color space is defined in [19]
CIELAB use for fax is described in ITU T.42 [9]
- 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.
- Security considerations:
- 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.
- Related feature tags:
color [3]
color-space [this document]
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- Related media types or data formats:
TIFF-FX [7]
- Intended usage:
Internet fax
Color image scanning/rendering applications
- Author/Change controller:
IETF (Fax Working Group)
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A.7 Image file structure
- Media Feature tag name(s):
image-file-structure
- ASN.1 identifier associated with this feature tag:
[[[New assignments by IANA]]]
- 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.).
- Values appropriate for use with this feature tag:
Token
TIFF-FX profiles TIFF-S
[7]: TIFF-F
TIFF-J
TIFF-C
TIFF-L
TIFF-M
(may be extended by further registrations,
to cover non-TIFF image file structures)
- 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.
- Examples of typical use:
See Appendix B of this memo.
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- 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.
In the case of TIFF-FX image data, there are a number of image
file format constraints that are imposed by the various usage
profiles defined in RFC 2301 [7]. The purpose of the 'image-
file-structure' feature tag is to capture those file format
constraints.
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.
- Related feature tags:
image-coding [this document]
- Related media types or data formats:
TIFF-FX [7]
TIFF V6.0 (Adobe) [20]
- Intended usage:
Internet fax
Image scanning/rendering applications
- Author/Change controller:
IETF (Fax Working Group)
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A.8 Image data coding
- Media Feature tag name(s):
image-coding
- ASN.1 identifier associated with this feature tag:
[[[New assignments by IANA]]]
- Summary of the media features indicated:
This feature tag indicates a form of image data compression
and coding used.
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.
- Values appropriate for use with this feature tag:
Token MH
MR
MMR
JBIG
JPEG
(may be extended by further registrations)
- 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.
- Examples of typical use:
See Appendix B of this memo.
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- 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]
- 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.
- Related feature tags:
image-coding-constraint [this document]
JBIG-stripe-size [this document]
image-interleave [this document]
- Related media types or data formats:
TIFF-FX [7]
- Intended usage:
Internet fax
Image scanning/rendering applications
- Author/Change controller:
IETF (Fax Working Group)
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A.9 Image coding constraint
- Media Feature tag name(s):
image-coding-constraint
- ASN.1 identifier associated with these feature tags:
[[[New assignments by IANA]]]
- 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.
- 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)
- 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.
- Examples of typical use:
See Appendix B of this memo.
- Related standards or documents:
JBIG-T85: ITU T.85 [18]
JBIG-T43: ITU T.43 [10]
JPEG-T4E: ITU T.4 Annex E [13]
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- 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.
- Related feature tags:
image-coding [this document]
JBIG-stripe-size [this document]
image-interleave [this document]
- Related media types or data formats:
TIFF-FX [7]
- Intended usage:
Internet fax
Color image scanning/rendering applications
- Author/Change controller:
IETF (Fax Working Group)
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A.10 JBIG stripe size
- Media Feature tag name(s):
JBIG-stripe-size
- ASN.1 identifier associated with these feature tags:
[[[New assignments by IANA]]]
- 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.
- Values appropriate for use with this feature tag:
Integer (>0)
- 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.
- Examples of typical use:
(JBIG-stripe-size=128)
(JBIG-stripe-size>0)
- Related standards or documents:
JBIG: ITU T.82 [17]
JBIG-T85: ITU T.85 [18]
JBIG-T43: ITU T.43 [10]
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- 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.
- 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.
- Related feature tags:
image-coding [this document]
image-coding-constraint [this document]
image-interleave [this document]
- Related media types or data formats:
TIFF-FX [7]
- Intended usage:
Internet fax
Color image scanning/rendering applications
- Author/Change controller:
IETF (Fax Working Group)
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A.11 Image interleave
- Media Feature tag name(s):
image-interleave
- ASN.1 identifier associated with this feature tag:
[[[New assignments by IANA]]]
- 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.
- Values appropriate for use with this feature tag:
Token Stripe
Plane
- 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.
- Examples of typical use:
(image-interleave=stripe)
(image-interleave=[stripe,plane])
- 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 render the
image. This may place considerable demands on the memory of a
sending or receiving system.
- Related feature tags:
image-coding [this document]
JBIG-stripe-size [this document]
- Related media types or data formats:
TIFF-FX [7]
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- Intended usage:
Internet fax
Color image scanning/rendering applications
- Author/Change controller:
IETF (Fax Working Group)
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A.12 Color subsampling
- Media Feature tag name(s):
color-subsampling
- ASN.1 identifier associated with this feature tag:
[[[New assignments by IANA]]]
- Summary of the media features indicated:
This feature tag indicates whether color information may be
subsampled with respect to luminance data.
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.
- 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 a set of color samples
for each luminance sample.
(may be extended by further registrations)
- 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.
- Examples of typical use:
(& (color=full) (color-space=[LAB,CIALAB])
(color-subsampling=["1:1:1","4:1:1"]) )
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- Related feature tags:
color [3]
color-space [this document]
image-file-structure [this document]
- Related media types or data formats:
TIFF-FX [7]
- Intended usage:
Internet fax
Color image scanning/rendering applications
- Author/Change controller:
IETF (Fax Working Group)
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A.13 MRC availability and mode
- Media Feature tag name(s):
MRC-mode
- ASN.1 identifier associated with this feature tag:
[[[New assignments by IANA]]]
- 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 and declared image-coding
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.).
- Values appropriate for use with this feature tag:
Integer (0..7)
- 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.
- Examples of typical use:
See Appendix B of this document.
- Related standards or documents:
ITU T.44 [15]
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- 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.
- Related feature tags:
image-coding [this document]
MRC-maximum-stripe-size [this document]
- Related media types or data formats:
TIFF-FX [7]
- Intended usage:
Internet fax
Color image scanning/rendering applications
- Author/Change controller:
IETF (Fax Working Group)
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A.14 MRC maximum stripe size
- Media Feature tag name(s):
MRC-maximum-stripe-size
- ASN.1 identifier associated with this feature tag:
[[[New assignments by IANA]]]
- 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.
- Values appropriate for use with this feature tag:
Integer (>0)
- 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.
- Examples of typical use:
(MRC-maximum-stripe-size=[0..256])
(MRC-maximum-stripe-size>=0)
- 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.
- Related feature tags:
MRC-mode [this document]
- Related media types or data formats:
TIFF-FX [7]
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- Intended usage:
Internet fax
Color image scanning/rendering applications
- Author/Change controller:
IETF (Fax Working Group)
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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.
(Tiff-S) :-
(& (image-file-structure=TIFF-S)
(color=Binary)
(image-coding=MH) (MRC-mode=0) )
(Tiff-F) :-
(& (image-file-structure=TIFF-F)
(color=Binary)
(image-coding=[MH,MR,MMR]) (MRC-mode=0) )
(TIFF-J) :-
(& (image-file-structure=TIFF-J)
(color=Binary)
(image-coding=JBIG) (MRC-mode=0) )
(TIFF-C) :-
(& (image-file-structure=TIFF-C)
(color=[Grey,Full])
(image-coding=JPEG) (MRC-mode=0) )
(TIFF-L) :-
(& (image-file-structure=TIFF-L)
(color=[Limited,Mapped,Grey,Full])
(image-coding=[JPEG,JBIG]) (MRC-mode=0) )
(TIFF-M) :-
(& (image-file-structure=TIFF-M)
(color=[Binary,Grey,Full])
(image-coding=[MH,JPEG]) (MRC-mode>=1) )
TIFF profile M is a composite structure that can combine image data
coding options from other profiles: the description above
indicates mandatory features; other options may be indicated by
combining TIFF-M with other options (color= limited or mapped, and
image-coding= MR, MMR or JBIG).
Support for multiple profiles is indicated by combining them with
the OR operator; e.g.
(| (TIFF-F) (TIFF-S) (TIFF-J) )
indicates support for all black-and-white modes.
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Appendix C: Revision history
00a 28-Sep-1998 Initial draft.
01a 12-Oct-1998 Incorporated review comments. Described feature
tag for differential x/y resolution ratio. Added
some examples.
01b 19-Oct-1998 Updated section 3.6 on image coding. Added
Appendix B containing feature expressions for the
TIFF modes from RFC 2301.
02a 26-Oct-1998 Update examples. Add separate stripe size
features for JBIG and MRC.
02b 30-Oct-1998 Update examples. Add text clarifying the
description of MRC documents (as a set of feature
collections describing multiple contained images).
Add text describing constrains on resolution and
image coding usage within an MRC document.
02c 11-Nov-1998 Add ITU references. Added terminology:
"capability exchange", "capability identification"
and "capability description". Update JBIG and MRC
stripe size tags. Move subsampling to colour
section. Remove preferred-unit tag. Add T.4,
T.6, T.44 and T.81 references.
02d 16-Nov-1998 Update colour handling features, reflecting
proposed changes to the media features memo [3].
Update the image coding capability framework.
Updated TIFF mode descriptions in Appendix B.
03a 17-Nov-1998 Replace use of 'pix-x', 'pix-y' with 'size-x',
'size-y'. Add registrations in Appendix A.
03b 08-Dec-1998 Remove normative language and reference to RFC2119
(normative statements will be in the main fax
protocol draft). Revise structure of colour
features, and removed color-palette feature.
Define colour feature tags specific to CIELAB
model and colour space.
04a 14-Dec-1998 Update examples to reflect revised feature tags.
Revise description of MRC document in section 3.7.
Remove Internet-draft boilerplate. Clarified
interpretation of 'color=fixed'. Change feature
value 'color=fixed' to 'color=limited'.
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| PAFTECH AB 2003-2026 | 2026-04-23 05:47:45 |