As per Relevance of the word indicate, we have this rfc below:
Network Working Group G.
Request for Comments: 2879 Content
Obsoletes: 2531 L.
Category: Standards Track Xerox
August 2000
Content Feature Schema for Internet Fax (V2)
Status of this
This document specifies an Internet standards track protocol for
Internet community, and requests discussion and suggestions
improvements. Please refer to the current edition of the "
Official Protocol Standards" (STD 1) for the standardization
and status of this protocol. Distribution of this memo is unlimited
Copyright
Copyright (C) The Internet Society (2000). All Rights Reserved
This document defines a content media feature schema for
fax
It is a profile of the media feature registration mechanisms [1,2,3]
for use in performing capability identification between
Internet fax systems [5]. It replaces and updates the feature
defined in RFC 2531.
Table of
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
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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.
This document defines a content media feature schema for
fax
It is a profile of the media feature registration mechanisms [1,2,3]
for use in performing capability identification between
Internet fax systems [5]. It replaces and updates the feature
defined in RFC 2531.
The media feature description mechanisms do not describe any
mechanisms for communicating capability information, but do
that any such mechanisms will transfer textual values.
conjunction with this feature schema, they specify a textual
to be used for describing Internet Fax capability information
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RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
The range of capabilities that can be indicated are based on
covered by the TIFF file format for Internet fax [7] and Group 3
facsimile [6]. A companion document [4] describes the
and mapping between this schema and Group 3 fax capabilities
1.1 Organization of this
Section 2 specifies the overall syntax for fax feature
by reference to the media feature registration and syntax
[1,2].
Section 3 enumerates the feature tags that are to be recognized
processed by extended Internet fax systems, according to
capabilities
Appendix A contains additional feature tag registrations for
features that are specific to fax and for which no
registration already exists. These are presented in the
prescribed by the media feature registration procedure [1].
1.2 Terminology and document
The term "extended Internet fax system" is used to describe
software, device or combination of these that conforms to
specification "Extended Facsimile Using Internet Mail" [5].
"capability exchange" describes any transfer of information
communicating systems that is used to indicate system
and hence determine the form of data transferred. This term
both one-way and two-way transfers of capability information
"capability identification" is a particular form of
exchange in which a receiving system provides capability
to a sending system
"capability description" is a collection of data presented in
specific format that describes the capabilities of some
entity. It may exist separately from any specific
exchange mechanism
NOTE: Comments like this provide additional
information about the rationale behind this document
Such information is not needed for building a
implementation, but may help those who wish to
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
Discussion of this document should take place on the Internet
mailing list hosted by the Internet Mail Consortium (IMC).
send comments regarding this document to
ietf-fax@imc.
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
list archive at
http://www.imc.org/ietf-fax
2. Fax feature schema
The syntax for the fax feature schema is described by "A syntax
describing media feature sets" [2]. This in turn calls upon
feature tags that may be registered according to the
described in "Media Feature Tag Registration Procedure" [1].
NOTE: Media feature registration provides a
vocabulary of features that correspond to media
capabilities. The feature set syntax provides
mechanism and format for combining these to
combinations of features. This memo indicates
features that may be associated with extended
fax systems
3. Internet fax feature
This section enumerates and briefly describes a number of
tags that are defined for use with extended Internet fax systems
applications. These tags may be used also by other systems
applications that support corresponding capabilities
The feature tags presented below are those that an extended
fax system is expected to recognize its ability or non-ability
handle
Definitive descriptions of feature tags are indicated by reference
their registration according to the media feature
procedure [1] (some of which are appended to this document).
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RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
NOTE: The presence of a feature tag in this list
not mean that an extended Internet fax system must
that capability; rather, it must recognize the
tag and deal with it according to the capabilities
it does have
Further, an extended Internet fax system is not
from recognizing and offering additional feature tags
The list below is intended to provide a basic
that all extended Internet fax systems can use in
consistent fashion
If an unrecognized or unused feature tag is received,
feature set matching rule (described in [2]) operates
that tag is effectively ignored
3.1 Image
Feature tag name Legal
---------------- ------------
size-x (>0)
size-y (>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
factor of 10/254 may be applied to yield an exact inch-based value
3.2
Feature tag name Legal
---------------- ------------
dpi (>0)
dpi-xyratio (>0)
Reference: "Media Features for Display, Print, and Fax" [3], and
document appendix A
If 'dpi-xyratio' is present and not equal to 1 then the
resolution (x-axis) is indicated by the 'dpi' feature value, and
vertical resolution (y-axis) is the value of 'dpi' divided by 'dpi
xyratio'.
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RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
For example, the basic Group 3 fax resolution of 200*100dpi might
indicated as
(& (dpi=200) (dpi-xyratio=200/100) )
When describing resolutions for an MRC format document, the
set of usable resolutions is listed. However, there are
restrictions on their use: (a) 100dpi resolution can be used
with multi-level images, and (b) any multi-level image resolution
required to be an integral sub-multiple of the applicable
resolution
3.3 Media
Feature tag name Legal
---------------- ------------
ua-media
screen-
envelope-
Reference: "Media Features for Display, Print, and Fax" [3].
NOTE: Where the recipient indicates specific support
hard copy or soft copy media type, a sender of
image data may wish to adjust the color components (e.g
per the related rules of ITU recommendation T.42 [9])
improve rendered image quality on that medium
3.4 Paper
Feature tag name Legal
---------------- ------------
paper-size A
A
B
Reference: "Media Features for Display, Print, and Fax" [3].
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RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
3.5 Color
Feature tag name Legal
---------------- ------------
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
capabilities that might be used, for example, to select among a
number of available data resources
The value of this feature also gives an indication of the
detailed color handling features that might be applicable (see
section).
'Binary' indicates blank-and-white, or other bi-level capability.
further qualifying feature tags are required
'Limited' indicates a small number of distinct fixed colors, such
might be provided by a highlight printer, pen plotter or
color display. The 'color-levels' tag should be used to indicate
number of distinct colors available
NOTE: No ability to indicate any specific or named
is implied by this option. Some devices might
different intensity levels rather than different hues
distinction
In the context of Internet fax, 'limited' is interpreted as one-bit
per-color-sample (RGB, CMY or CMYK), depending on the color
used
'Mapped' indicates that pixel color values are mapped in
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
should be assumed
'Grey' indicates a continuous tone grey-scale capability
'Full' indicates full continuous tone color capability
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RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
For 'Mapped', 'Grey' and 'Full' color, additional feature
(section 3.6) may be used to further qualify the color reproduction
3.6 Color
Feature tag name Legal
---------------- ------------
color-levels (>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 (per ITU T.4 [13], E.6.7)
D50
D65
D75
F
F
F11
CTnnnn (see below
CIELAB-L-depth (>0)
CIELAB-a-depth "
CIELAB-b-depth "
CIELAB-L-min
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)
described here from a receiver's perspective; a similar
operates in the reverse direction for a scan/send perspective
raw bit pixel color
stream -(A)-> values -(B)-> values -(C)->
- "raw bit stream" is a stream of coded
(A) indicates image coding/decoding (MH,MR,MMR,JPEG,JBIG,etc.)
- "pixel values" are a single numeric value per picture
that designates the color of that element
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RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
(B) indicates pixel-to-color value
- "color values" have a separate numeric value for each
component (i.e. L*, a*, b* in the case of CIELAB
above.)
(C) indicates how the color values are related to a
color. This involves interpretation of the color value
respect to a color model (e.g. RGB, L*a*b*, CMY, CMYK) and
color space (which is typically recipient-dependent).
- "physical rendition" is a color value physically realized on
display, printer or other device
There are many variables that can be applied at each stage of
processing of a color image, and any may be critical to
handling of that image in some circumstances. In other
many of the variables may be implied (to some level of approximation
in the application that uses them (e.g. color images published on
Web page).
The color feature framework described here is intended to
capability description at a range of granularity: feature tags
correspond to implied (or "don't care" or "unknown") feature
may simply be omitted from a capability description
Grey scale and bi-level images are handled within this framework as
special case, having a 1-component color model. The
features are used for describing color capabilities
'color-levels' indicates the number of distinct values for
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
used with other modes if the exact color or color model used
significant. Two kinds of color space can be distinguished
device-dependent and calibrated. Device dependent spaces are
here as 'Device-xxx', and are used to indicate a color space that
defined by the receiving device. Calibrated color spaces presume
existence of a rendering system that is calibrated with respect to
indicated definition, and is capable of processing the device
independent color information accordingly
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RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
A color-handling receiver should indicate any appropriate
color space capability in addition to any calibrated color
that it may support. A calibrated color space should be used
precise color matching is required in the absence of
knowledge of the receiving system
NOTE: In practice, although they appear to be
concepts, the color model and color space cannot
separated. In the final analysis, a color model (RGB
CMY, etc.) must be defined with respect to some
space
'color-illuminant' indicates a CIE illuminant, using the same
form that is used for this purpose by Group 3 fax (as defined in
T.4 [13], section E.6.7). When the illuminant is specified by
color temperature, the token string 'CTnnnn' is used, where 'nnnn'
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
temperature values
In practice, much of the illuminant detail given
will probably be unused by Internet fax. The only
likely to be specified is 'D50', which is the
color illuminant for Group 3 fax
'CIELAB-L-depth', 'CIELAB-a-depth' and 'CIELAB-b-depth' indicate
number of different values that are possible for the L*, a* and b
color components respectively, and are significant only when
are represented in a CIELAB color space. These features would
used with palletized color, or with full color where each
component has a different number of possible values
Color depth values relate to the representation of colour
rather than the resolution of a scanning or rendering device. Thus
if 256 different L-component values can be represented then
assertion (CIELAB-L-depth<=256) is used, even if a receiving
can render only 100 distinct luminance values. (Color
resolution is not covered by this memo.)
The 'CIELAB-x-min' and 'CIELAB-x-max' values indicate a color
(i.e. a range of color values that are used or may be rendered).
gamut may be indicated in terms of the CIELAB color space even
colors are represented in some other space
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RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
3.7 Image
Feature tag name Legal
---------------- ------------
image-file-
structure TIFF-
TIFF-
TIFF-
TIFF-MRC-
(may be extended by further registrations
image-coding
(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
image-interleave
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
and formatted. The following options are defined here
o 'TIFF' indicates image data enclosed and tagged using
structures described in Adobe's definition of TIFF [20].
o 'TIFF-limited' indicates image data structured using TIFF,
with the limitations on the placement of Image File
(IFDs) indicated in section 4.4.6 of RFC 2301 [7].
o 'TIFF-minimal' indicates a TIFF image format that meets the
placement, byte ordering and bit ordering requirements of
"minimal black and white mode" described in section 3.5 of
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"
section 8.1.2 of RFC 2301 [7], also known as TIFF-M.
provides a file structure to contain composite images
using the MRC model described in T.44 [15] (see tag 'MRC-mode').
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RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
o 'TIFF-MRC-limited' is the same as 'TIFF-MRC', except that
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
as a sequence of bits. These are generic tags that may apply to
range of file formats and usage environments
'image-coding-constraint' describes how the raw image data
method is constrained to meet a particular operating environment
Options defined here are JBIG and JPEG coding constraints that
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
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,
not all are required in all circumstances
Specification of the image-file-structure tag value
is not normally sufficient to describe the
of a recipient. A general rule is that sufficient
should be provided to exclude any unsupported features
For extended Internet fax, image-file-structure
image-coding should always be specified, together
additional values described above as needed to
indicate which feature tag values are supported and
are not. (See also the examples in section 4.)
3.8 MRC
Feature tag name Legal
---------------- ------------
MRC-mode (0..7) (per ITU T.44 [15])
MRC-max-stripe-size
Reference: this document, appendix A
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RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
The 'MRC-mode' feature is used to indicate the availability of
(mixed raster content) image format capability. A zero
indicates MRC is not available, a non-zero value indicates
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.
MRC-capable receiver is presumed to be capable of accepting
combination of contained images that conform to both the
construction rules and the image-coding capabilities
elsewhere
Within an MRC-formatted document, multi-level coders are used
foreground and background images (i.e. odd-numbered layers: 1, 3, 5,
etc.) and bi-level coders are used for mask layers (i.e.
numbered layers 2, 4, 6, etc.). MRC format also imposes
on the resolutions that can be used
The 'MRC-max-stripe-size' feature may be used with MRC coding,
indicates the maximum number of scan lines in each MRC stripe.
legal constraints are
(MRC-max-stripe-size<=256)
(MRC-max-stripe-size>=0)
These values indicate upper bounds on the stripe size. The
value may vary between stripes, and the actual size for each
is indicated in the image data
4.
The level of detail captured here reflects that used for
identification in Group 3 facsimile
4.1 Simple mode Internet fax
This example describes the capabilities of a typical simple
Internet fax system. Note that TIFF profile S is required to
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)
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RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
(ua-media=stationery) )
4.2 High-end black-and-white Internet fax
This would include support for B/W JBIG and be equivalent to what
sometimes called "Super G3", except that Internet fax
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
This is the previous example extended to handle grey scale multi
level images. In keeping with Group 3 fax, this example
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)
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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) )
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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
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)
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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
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
in three possible formats, A4 high resolution, B4 low resolution
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
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
this point
The composite document description can be matched with the
capability description, according to the rules in [2], to yield
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
cannot handle either color (indicated by '(color=Mapped)')
JPEG coding (indicated by '(image-coding=JPEG)').
o The high resolution version of the document with '(dpi=300)'
be send using '(image-coding=JBIG)' because this is the
available coding of the image data that the receiver can use
high resolution documents. (The available 300dpi
codings here are MMR and JBIG, and the receiver capabilities
MH, MR and JBIG.)
o The low-resolution version of the document can be sent
either MH or MR coding as the receiver can deal with either
these for low resolution documents
o The high resolution variant of the document is available only
A4, so that is the paper-size used in that case. Similarly
low resolution version is sent for B4 paper
o Even though the sender may not understand the 'ua-media'
tag, and does not mention it, the matching rules preserve
Klyne & McIntyre Standards Track [Page 20]
RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
constraint that the B4 document is rendered
'(ua-media=continuous)', and the A4 document may be rendered
'(ua-media=[stationery,transparency])'.
Finally, note that when matching an MRC document description,
description of each component sub-image must match the
of the intended receiver
5. IANA
Appendix A of this document repeats the descriptions of feature
introduced by RFC 2531 [22], with some small revisions. These
been registered in the "IETF tree", according to the
described in section 3.1.1 of "Media Feature Tag
Procedure" [1] (i.e. these feature tags are subject to the "
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.
ASN.1 identifier should be assigned for this new tag and replaced
the body of the registration
6. Security
The points raised below are in addition to the general
considerations for extended Internet fax [5], and others discussed
[2,8,11,12,13]
6.1 Capability descriptions and
Negotiation mechanisms reveal information about one party to
parties. This may raise privacy concerns, and may allow a
party to make better guesses about the presence of specific
holes
Most of these concerns pertain to capability information getting
the hands of someone who may abuse it. This document
capabilities that help a sender to determine what
characteristics can be processed by the recipient, not mechanisms
their publication. Implementers and users should take care that
mechanisms employed ensure that capabilities are revealed only
appropriate persons, systems and agents
6.2 Specific
1. Unsolicited bulk mail: if it is known that a recipient
process certain types of images, they may be targeted by
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.
The authors gratefully acknowledge the contributions of the
persons who commented on earlier versions of this memo:
Rafferty, Dan Wing, Robert Buckley, Mr Ryuji Iwazaki. The
contributed ideas upon which some of the features described here
been based: Larry Masinter, Al Gilman, Koen Holtman
8.
[1] Holtman, K., Mutz, A. and T. Hardie, "Media Feature
Registration Procedure", RFC 2506, March 1999.
[2] Klyne, G., "A syntax for describing media feature sets",
2533, March 1999.
[3] Masinter, L., Holtman, K., Mutz, A. and D. Wing, "Media
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
Internet Mail", RFC 2532, March 1999.
[6] "Procedures for document facsimile transmission in the
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,
1998.
[8] Toyoda, K., Ohno, H., Murai, J. and D. Wing, "A Simple Mode
Facsimile Using Internet Mail", RFC 2305, March 1998.
[9] "Continuous-tone color representation method for facsimile
ITU-T Recommendation T.42 (1996)
Telecommunications Union (Covers custom illuminant, gamut
[10] "Colour and gray-scale image representation using
coding scheme for facsimile" ITU-T Recommendation T.43 (1997)
International Telecommunications Union. (Covers JBIG
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
transmission", ITU-T Recommendation T.4 (1999),
Telecommunications Union, (Covers basic fax coding formats: MH
MR
[14] "Facsimile coding schemes and coding control functions for
4 facsimile apparatus", ITU Recommendation T.6,
Telecommunications Union, (Commonly referred to as the
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
continuous-tone still image - Requirements and guidelines" ITU-
Recommendation T.81 (1992) | ISO/IEC 10918-1:1993
Telecommunications Union, (Commonly referred to as
standard
[17] "Information technology - Coded representation of picture
audio information - Progressive bi-level image compression
ITU-T Recommendation T.82 (1993) | ISO/IEC 11544:1993
International Telecommunications Union (Commonly referred to
JBIG1 standard
[18] "Application profile for Recommendation T.82 - Progressive bi
level image compression (JBIG1 coding scheme for
apparatus)", ITU-T Recommendation T.85 (1995),
Telecommunications Union, (Covers bi-level JBIG).
[19] "Colorimeter, 2nd ed.", CIE Publication No. 15.2, 1986. (
CIELAB color space; use with fax is further constrained by T.42
[9].)
[20] Tag Image File Format, Revision 6.0 Adobe Developers
/tiff6.pdf> June 1992
[21] Narten, T. and H. Alvestrand, "Guidelines for Writing an
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[22] Klyne, G. and L. McIntyre, "Content feature schema for
fax", RFC 2531, March 1999.
Klyne & McIntyre Standards Track [Page 23]
RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
9. Authors'
Graham
Content Technologies Ltd
1220 Parkview
Arlington Business
Reading, RG7 4
United Kingdom
Phone: +44 118 930 1300
Fax: +44 118 930 1301
EMail: GK@ACM.
Lloyd
Xerox
Mailstop PAHV-121
3400 Hillview Ave
Palo Alto, CA 94304
Phone: +1-650-813-6762
Fax: +1-650-845-2340
EMail: Lloyd.McIntyre@pahv.xerox.
Klyne & McIntyre Standards Track [Page 24]
RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
Appendix A: Feature
A.1 Image
- Media Feature tag name(s):
size-
size-
- 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
- Summary of the media features indicated
These feature tags indicate the size of a displayed,
or otherwise rendered document image; they
horizontal (size-x) and vertical (size-y) dimensions
The unit of measure is inches (to be consistent with
measure of resolution defined by the feature tag 'dpi').
Where the actual size is available in millimetres,
conversion factor of 10/254 may be applied to yield an
inch-based value
- Values appropriate for use with these feature tags
Rational (>0)
- The feature tag is intended primarily for use in the
applications, protocols, services, or negotiation mechanisms
Print and display applications where different media
will be made depending on the size of the recipient device
- Examples of typical use
This example describes the maximum scanned image width
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
- Related standards or documents
The memo "Media Features for Display, Print, and Fax" [3]
describes features (pix-x, pix-y) for measuring document
in pixels
Fax applications should declare physical dimensions using
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
is known, a notional size should be declared based upon
pixel dimensions and a notional resolution of (say) 100
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
fairly typical resolution for a pixel-limited display
Reducing the rational numbers to canonical form gives
following equivalent expression
(& (size-x<=32/5) (size-y<=24/5) (dpi=100) )
- Interoperability considerations
For interoperability with other (non-fax) applications
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
Klyne & McIntyre Standards Track [Page 26]
RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
- Author/Change controller
A.2 Resolution aspect
- Media Feature tag name(s):
dpi-
- ASN.1 identifier associated with this feature tag
1.3.6.1.8.1.9
- Summary of the media features indicated
This feature is used to indicate differential horizontal
vertical resolution capability. In the absence of
feature, horizontal and vertical resolutions are presumed
be the same
When this feature tag is specified, any declared
(dpi) is presumed to apply to the horizontal axis, and
vertical resolution is obtained by dividing that
resolution by the resolution ratio
The value of this feature is a pure number, since
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
applications, protocols, services, or negotiation mechanisms
Internet fax, and other print or display applications
must handle differential horizontal and vertical
values
- Examples of typical use
The following example describes a fax resolution of 204
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
- Related standards or documents
The memo "Media Features for Display, Print, and Fax" [3]
describes a feature (dpi) for measuring document resolution
- Interoperability considerations
When interoperating with an application that does
recognize the differential resolution feature,
matching may be performed on the basis of the
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
- Author/Change controller
A.3 Color
- Media Feature tag name(s):
color-
- ASN.1 identifier associated with this feature tag
1.3.6.1.8.1.10
- Summary of the media features indicated
This feature tag is used to indicate a number of
image data pixel color values
When mapped (palletized) color is used, this is
different from the number of different colors that can
represented through the color mapping function
This feature tag is used in conjunction with a 'color'
having a value other than 'Binary'.
Klyne & McIntyre Standards Track [Page 28]
RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
- Values appropriate for use with this feature tag
Integer (>=2)
- The feature tag is intended primarily for use in the
applications, protocols, services, or negotiation mechanisms
Color image printing or display applications where the
resource used may depend upon color handling capabilities
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) )
- Related standards or documents
The memo "Media Features for Display, Print, and Fax" [3]
describes a feature (color) for indicating basic
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
recipient. To achieve a feature match, at least one must
declared as an inequality (i.e. not both as equalities).
It is recommended that a recipient declares the number
color values that it can handle as an inequality (<=), and
data resource declares the number of colors that it uses
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
- Security considerations
- Privacy concerns, related to exposure of personal information
Where feature matching is used to select content
to the physical abilities of a user, unusual values for
feature tag might give an indication of a user's
abilities
- Related feature tags
color [3]
color-space [this document
- Intended usage
Internet
Color image scanning/rendering
- Author/Change controller
A.4 Color
- Media Feature tag name(s):
color-
- ASN.1 identifier associated with this feature tag
1.3.6.1.8.1.11
- 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,
the number of color
o a mapping between color values and their
Device color space values are defined for applications
the general color representation used is significant,
exact color rendering is left to the device used.
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
rendering system that is calibrated with respect to
indicated definition, and capable of processing device
independent color information accordingly
- Values appropriate for use with this feature tag
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
white point (per T.42 [9]).
- The feature tag is intended primarily for use in the
applications, protocols, services, or negotiation mechanisms
Color image printing and display applications where the
resource used may depend upon color handling capabilities
the recipient
Scanning applications where the data transferred may
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
approximate color reproduction is required
(color-space=Device-RGB
To describe capabilities assumed by a document for which
color reproduction is required
(color-space=CIELAB
Klyne & McIntyre Standards Track [Page 31]
RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
- 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 any
device color space capability, in addition to any
color spaces that it may support
Calibrated color spaces are intended to be used when
color matching is required; otherwise, if applicable,
device color space (color-space=Device-xxx) should
indicated
Documents for which exact color matching is not
should indicate a device color space capability,
applicable
These principles allow sender/receiver feature matching to
achieved when exact color matching is not required
- Security considerations
- Privacy concerns, related to exposure of personal information
Where feature matching is used to select content
to the physical abilities of a user, unusual values for
feature tag might give an indication of a user's
abilities
- Denial of service concerns related to consequences
specifying incorrect values
Failure to indicate a generic color space capability for
device may lead to failure to match color space for
application or document that does not require an exact
match
- Related feature tags
color [3]
- 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
- Intended usage
Internet
Color image scanning/rendering
- Author/Change controller
A.5 CIELAB color
- Media Feature tag name(s):
color-
- ASN.1 identifier associated with this feature tag
1.3.6.1.8.1.29
- Summary of the media features indicated
This feature indicates a color illuminant. This has
effect of modifying the color space calibration to reflect
use of different sources of illumination
A color-illuminant value would normally be used only with
calibrated color space
- Values appropriate for use with this feature tag
CIELAB illuminant D50
values: D65
D75
F
F
F11
Defined by color CTnnnn where 'nnnn' is a
temperature: representation of the
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.
- The feature tag is intended primarily for use in the
applications, protocols, services, or negotiation mechanisms
Color image printing and display applications where the
resource used may depend upon detailed color
capabilities of the recipient
Scanning applications where the data transferred may
upon the image generation capabilities of the originator
- Examples of typical use
To describe rendering or scanning capabilities, or to
capabilities assumed by a document for which exact
handling capabilities are required
(& (color-space=CIELAB) (color-illuminant=D50) )
- Related standards or documents
CIELAB color illuminant representations are described in
T.4 [13], Annex E.6.7.
- Interoperability considerations
A color-handling receiver that supports a calibrated
space should indicate any constraint on the illuminants it
handle
In the absence of a color-illuminant constraint, a receiver
presumed to accept and deal with any specified
value
- Related feature tags
color [3]
color-space [this document
- Related media types or data formats
TIFF-FX [7]
- Intended usage
Internet
Color image scanning/rendering
Klyne & McIntyre Standards Track [Page 34]
RFC 2879 Content Feature Schema for Internet Fax (V2) August 2000
- Author/Change controller
A.6 CIELAB color
- Media Feature tag name(s):
CIELAB-L-
CIELAB-a-
CIELAB-b-
- 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
- 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
component can be specified. They define the number
distinct values possible for each of the color components L*,
a* and b*.
Typically, this feature would be used with 'color=mapped',
possibly 'color=grey' or 'color=full', to indicate the
of distinct colors that can be represented
NOTE: this feature tag describes the number of values
can be represented for a color component, and does
necessarily indicate the number of distinct values that
be rendered or resolved by a system
- Values appropriate for use with these feature tags
Integer (>0)
- These feature tags are intended primarily for use in
following applications, protocols, services, or
mechanisms
Color image printing and display applications where the
resource used may depend upon color handling capabilities
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
upon the image generation capabilities of the originator