IETF Fax working group Graham Klyne INTERNET DRAFT 5GM/Content Technologies Category: Work-in-progress Lloyd McIntyre Xerox Corporation 17 November 1998 Expires: May 1999 Content feature schema for Internet fax Status of this memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as ``work in progress''. To view the entire list of current Internet-Drafts, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). [[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.]] 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]. Klyne/McIntyre Work-in-progress [Page 1] RFC nnnn Content feature schema for Internet fax 17 November 1998 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. Table of contents 1. Introduction ............................................3 1.1 Organization of this document 3 1.2 Terminology and document conventions 3 1.3 Revision history 4 1.4 Unfinished business 5 2. Fax feature schema syntax ...............................5 3. Internet fax feature tags ...............................5 3.1 Image size 6 3.2 Resolution 6 3.3 Media type 7 3.4 Paper Size 7 3.5 Colour capability 8 3.6 Colour model 8 3.7 Image coding 11 4. Examples ................................................12 4.1 Simple mode Internet fax system 13 4.2 High-end black-and-white Internet fax system 13 4.3 Grey-scale Internet fax system 14 4.4 Full-colour Internet fax system (JPEG) 15 4.5 Full-colour Internet fax system (MRC) 15 4.6 Sender and receiver feature matching 16 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 ......................................21 Appendix A: Feature registrations ..........................22 A.1 Image size 22 A.2 Resolution aspect ratio 24 A.3 Colour levels 26 A.4 Colour resolution 28 A.5 Colour space 30 A.6 Colour palette 33 A.7 Colour illuminant 35 A.8 Colour gamut 37 A.9 Colour subsampling 40 A.10 Image file structure 42 A.11 Image data coding 44 A.12 Image coding constraint 46 A.13 JBIG stripe size 48 Klyne/McIntyre Work-in-progress [Page 2] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.14 Image interleave 50 A.15 MRC availability and mode 52 A.16 MRC maximum stripe size 54 Appendix B: TIFF mode descriptions .........................56 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 key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 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]. Klyne/McIntyre Work-in-progress [Page 3] RFC nnnn Content feature schema for Internet fax 17 November 1998 "capability exchange" describes any transfer of information between communicating systems that is used to indicate system capabilities and hence determine the form of data transferred. This term covers both one-way and two-way transfers of capability information. "capability identification" is a particular form of capability exchange in which a receiving system provides capability information to a sending system. "capability description" is a collection of data presented in some specific format that describes the capabilities of some communicating entity. It may exist separately from any specific capability exchange mechanism. NOTE: Comments like this provide additional nonessential information about the rationale behind this document. Such information is not needed for building a conformant implementation, but may help those who wish to understand the design in greater depth. 1.3 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. Klyne/McIntyre Work-in-progress [Page 4] RFC nnnn Content feature schema for Internet fax 17 November 1998 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. 1.4 Unfinished business - Review terminology (especially eifax). - Review examples in light of final media-feature tags - Locate appropriate references for esoteric colour features - Resolve queries raised in the feature tag registrations 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 that may be handled by 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 'conneg' 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. Klyne/McIntyre Work-in-progress [Page 5] RFC nnnn Content feature schema for Internet fax 17 November 1998 Further, an eifax system is not prevented from recognizing and offering additional feature tags. The list below is intended to provide a minimum vocabulary that all eifax systems can use in a consistent fashion. If an unrecognized or unused feature tag is received, the feature set matching rule (described in [2]) operates so that tag is effectively ignored. 3.1 Image size Feature tag name Legal values ---------------- ------------ size-x (>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 conversion factor of 10/254 may be applied to yield an exact inch-based value. 3.2 Resolution Feature tag name Legal values ---------------- ------------ dpi (>0) dpi-xyratio (>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. Klyne/McIntyre Work-in-progress [Page 6] RFC nnnn Content feature schema for Internet fax 17 November 1998 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 colour image data may wish to adjust the colour components (e.g. per the related rules of ITU recommendation T.42 [9]) to improve rendered image quality on that medium. 3.4 Paper Size Feature tag name Legal values ---------------- ------------ paper-size A4 A3 B4 letter legal Reference: "Media Features for Display, Print, and Fax" [3]. Klyne/McIntyre Work-in-progress [Page 7] RFC nnnn Content feature schema for Internet fax 17 November 1998 3.5 Colour capability Feature tag name Legal values ---------------- ------------ color None (bi-level only) Fixed (small number of fixed colours) Grey (grey-scale only) Mapped (palette or otherwise mapped colour) Full (full continuous-tone colour) Reference: "Media Features for Display, Print, and Fax" [3]. The intention here is to give a broad indication of colour 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 colour handling features that might be applicable (see next section). 3.6 Colour model Feature tag name Legal values ---------------- ------------ color-levels (>2) color-resolution (>0) color-space Generic colour spaces: RGB (generic RGB) LAB (generic L*a*b*) CMY (generic CMY) CMYK (generic CMYK) Specific colour spaces: CIELAB (LAB per T.42 [9]) (may be extended by further registrations) color-palette Custom ITU-T43 (per T.43 [10]) (may be extended by further registrations) color-illuminant Custom CIED50 ([[[reference???]]]) (may be extended by further registrations) color-gamut "lo1..hi1,lo2..hi2, ... ,loN..hiN" "Video" [[[reference to be supplied]]] "Hardcopy" [[[reference to be supplied]]] (may be extended by further registrations) Reference: this document, appendix A. Klyne/McIntyre Work-in-progress [Page 8] RFC nnnn Content feature schema for Internet fax 17 November 1998 [[[GK: what about tokens for intensity/hue/saturation, and composite-video-style Luminance and two colour- difference signals???]]] The general model for image handling (both colour and non-colour) is described here from a receiver's perspective; a similar model operates in the reverse direction for a scan/send perspective: raw bit pixel colour 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 pixel (B) indicates pixel-to-colour value mapping - "colour values" have a separate numeric value for each colour component (typically, 1, 3 or 4 components) (C) indicates how the colour values are related to a physical colour, and involves interpretation of the colour value with respect to a colour model (e.g. RGB, LAB, CMY, CMYK) and a colour space (which is typically device-dependent). - "physical rendition" is a colour value physically realized on a display, printer or other device. There are very many variables that can be applied at each stage of the processing of a colour image, and any one 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. colour images published on a Web page). Grey scale and bi-level images are handled within this framework as a special case, having a 1-component colour model. The following features are suggested for describing color capabilities: 'color-levels' indicates the number of distinct values for each pixel, and applies to all but bi-level images. For bi-level images, a value of 2 is implied. 'color-resolution' indicates the number of different colour values that can be rendered or physically represented. This value is generally the same as 'color levels' except for 'Mapped' (palettized) colour, and would not normally be specified other than in that case. Klyne/McIntyre Work-in-progress [Page 9] RFC nnnn Content feature schema for Internet fax 17 November 1998 'color-space' is used mainly with 'Mapped' and 'Full', but may be used with other modes if the exact colour used is significant. The generic colour spaces are used to indicate a broad colour capability colour value representation, without exactly specifying a physical realization for each colour values. Specific colour spaces are used for exact colour matching, and presume the existence of calibrated colour data and rendering systems. A colour-handling device should always indicate at least one generic colour space capability, in addition to any specific colour spaces that it may support. For a specific transaction, a generic colour space requirement should be indicated if that is sufficient for the purposes of the transaction; specific colour spaces are intended to be used only when precise colour matching is required. 'color-palette' is used only for 'mapped' colour, and gives an indication of the pixel-to-colour value mapping used. The 'color-illuminant' feature is generally used when precise colour matching is required. The value 'Custom' is used when details of the illuminant can be carried in an image data file. Other values refer to published specifications as indicated. The 'color-gamut' string indicates the range of colour component values that can be handled, either as a sequence of up to N component value ranges in the format given (where N depends upon the colour space used), or as a token that references an indicated published specification. For generic gamut matching, suitable selected tokenized values might be used (e.g. "Video", "Hardcopy"). Specific applications might understand the content of the gamut string and interpret expressions like: (color-gamut<="1..100,-75..75,-75..125") but this is not a required feature of the generic capability matching framework. Klyne/McIntyre Work-in-progress [Page 10] RFC nnnn Content feature schema for Internet fax 17 November 1998 3.7 Image coding Feature tag name Legal values ---------------- ------------ image-file- TIFF-S structure TIFF-F TIFF-J TIFF-L TIFF-C 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 image-interleave Stripe Plane color-subsampling "1:1:1" (no colour subsampling) "4:1:1" (4:1:1 colour subsampling) MRC-mode (0..7) (per ITU T.44 [15]) MRC-max-stripe-size 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. '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. Klyne/McIntyre Work-in-progress [Page 11] RFC nnnn Content feature schema for Internet fax 17 November 1998 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. Thus, an entire MRC document is characterized by a set of feature collections --a feature set-- that must be a subset of the capabilities of the message receiver. 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. 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. Klyne/McIntyre Work-in-progress [Page 12] RFC nnnn Content feature schema for Internet fax 17 November 1998 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. (& (dpi=200) (dpi-xyratio=[200/100,200/200]) (grey=2) (color=0) (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. (& (| (& (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 (grey=2) (color=0) (| (image-coding=[MH,MR,MMR]) (& (image-coding=JBIG-2-LEVEL) (JBIG-stripe-size=128) ) (MRC-mode=0) (paper-size=[A4,B4]) ) Klyne/McIntyre Work-in-progress [Page 13] RFC nnnn Content feature schema for Internet fax 17 November 1998 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. (& (| (& (grey=2) (color=0) (| (image-coding=[MH,MR,MMR]) (& (image-coding=JBIG-2-LEVEL) (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) ) ) ) (& (grey<=256) (color=0) (| (& (image-coding=JPEG) (color-space=CIELAB) ) (& (image-coding=JBIG-M-LEVEL) (JBIG-stripe-size=128) (color-space=Palette) (image-interleave=stripe) ) ) (| (& (dpi=200) (dpi-xyratio=1) ) (& (dpi=300) (dpi-xyratio=1) ) ) ) ) (MRC-mode=0) (paper-size=[A4,B4]) ) Klyne/McIntyre Work-in-progress [Page 14] RFC nnnn Content feature schema for Internet fax 17 November 1998 4.4 Full-colour Internet fax system (JPEG) This adds 16-bit full-colour to the previous example. (& (| (& (grey=2) (| (image-coding=[MH,MR,MMR]) (& (image-coding=JBIG-2-LEVEL) (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) ) ) ) (& (grey<=256 ) (color<=65536) (color-subsampling=[SS-1-1-1,SS-4-1-1]) (| (& (image-coding=JPEG) (color-space=CIELAB) ) (& (image-coding=JBIG-M-LEVEL) (JBIG-stripe-size=128) (color-space=Palette) (image-interleave=stripe) ) ) (| (& (dpi=200) (dpi-xyratio=1) ) (& (dpi=300) (dpi-xyratio=1) ) ) ) ) (MRC-mode=0) (paper-size=[A4,B4]) ) 4.5 Full-colour Internet fax system (MRC) (& (| (& (image-coding=[MH,MMR]) (MRC-mode=0) (| (& (dpi=200) (dpi-xyratio=[200/100,1,200/400]) ) (& (dpi=300) (dpi-xyratio=1) ) (& (dpi=400) (dpi-xyratio=1) ) ) (grey=2) (color=0) ) (& (image-coding=JPEG) (MRC-mode=0) (dpi=[100,200,300,400]) (dpi-xyratio=1) (grey<=256) (color<=65536) (color-space=CIELAB) (color-subsampling=[SS-1-1-1,SS-4-1-1]) (& (MRC-mode=1) (MRC-stripe-size=[0..256]) (image-coding=[MH,MMR,JPEG]) (grey<=256) (color<=65536) (color-space=CIELAB) (color-subsampling=[SS-1-1-1,SS-4-1-1]) (dpi=[100,200,300,400]) (dpi-xyratio=1) ) ) (paper-size=[A4,B4]) ) Klyne/McIntyre Work-in-progress [Page 15] RFC nnnn Content feature schema for Internet fax 17 November 1998 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 (grey=2) (color=0) (| (& (paper-size=A4) (ua-media=[stationery,transparency]) ) (& (paper-size=B4) (ua-media=continuous) ) ) (image-coding=[MH,MR,JBIG-2-LEVEL]) ) 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 colour, described by: (& (dpi=300) (dpi-xyratio=1) (grey=2) (paper-size=A4) (image-coding=[MMR,JBIG-2-LEVEL]) ) (& (dpi=200) (dpi-xyratio=200/100) (grey=2) (paper-size=B4) (image-coding=[MH,MR]) ) (& (dpi=300) (dpi-xyratio=1) (color<=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) (grey=2) (paper-size=A4) (image-coding=[MMR,JBIG-2-LEVEL]) ) (& (dpi=200) (dpi-xyratio=200/100) (grey=2) (paper-size=B4) (image-coding=[MH,MR]) ) (& (dpi=300) (dpi-xyratio=1) (color=42) (paper-size=A4) (image-coding=JPEG) ) ) Klyne/McIntyre Work-in-progress [Page 16] RFC nnnn Content feature schema for Internet fax 17 November 1998 This could be simplified, but there is little gain in doing so at this point. The composite document description can be matched with the receiver capability description, according to the rules in [2], to yield the result: (| (& (dpi=300) (dpi-xyratio=1) (grey=2) (paper-size=A4) (ua-media=[stationery,transparency]) (image-coding=JBIG-2-LEVEL) ) (& (dpi=200) (dpi-xyratio=200/100) (grey=2) (paper-size=B4) (ua-media=continuous) (image-coding=[MH,MR]) ) ) Points to note about the feature matching process: o The colour document option is eliminated because the receiver cannot handle either colour (indicated by '(color=0)') or JPEG coding. o The high resolution version of the document with '(dpi=300)' must be send using '(image-coding=JBIG-2-LEVEL)' 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-2-LEVEL, and the receiver capabilities are MH, MR and JBIG-2-LEVEL.) 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])'. Klyne/McIntyre Work-in-progress [Page 17] RFC nnnn Content feature schema for Internet fax 17 November 1998 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. Klyne/McIntyre Work-in-progress [Page 18] RFC nnnn Content feature schema for Internet fax 17 November 1998 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, [[...]]. 8. References [1] "Media Feature Tag Registration Procedure" Koen Holtman, TUE Andrew Mutz, Hewlett-Packard Ted Hardie, NASA Internet draft: Work in progress, July 1998. [2] "A syntax for describing media feature sets" Graham Klyne, 5GM/Content Technologies Internet draft: " 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: 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: Work in progress, August 1998. [5] "Extended Facsimile Using Internet Mail Larry Masinter, Xerox Corporation Dan Wing, Cisco Systems Internet draft: Work in progress, September 1998. Klyne/McIntyre Work-in-progress [Page 19] RFC nnnn Content feature schema for Internet fax 17 November 1998 [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 colour 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: Work in progress, November 1997. [12] "Requirements for protocol-independent content negotiation" G. Klyne, Integralis Ltd. Internet draft: 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) Klyne/McIntyre Work-in-progress [Page 20] RFC nnnn Content feature schema for Internet fax 17 November 1998 [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) 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-305 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 Klyne/McIntyre Work-in-progress [Page 21] RFC nnnn Content feature schema for Internet fax 17 November 1998 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 minimum scanned image width and height for Group 3 fax: 215x297 mm (8.46x11.69 inches): (size-x<=2150/254) (size-y<=2970/254) Klyne/McIntyre Work-in-progress [Page 22] RFC nnnn Content feature schema for Internet fax 17 November 1998 - 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.) - 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) Klyne/McIntyre Work-in-progress [Page 23] RFC nnnn Content feature schema for Internet fax 17 November 1998 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. Klyne/McIntyre Work-in-progress [Page 24] RFC nnnn Content feature schema for Internet fax 17 November 1998 - 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) Klyne/McIntyre Work-in-progress [Page 25] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.3 Colour 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 pixel values that can be represented by a document or image data. When grey-scale or mapped (palettized) colour is used, this may be different from the number of different colours that can be represented through the colour-mapping function. This feature tag is used in conjunction with the 'color' feature, with a value other than "None". It can be used with most kinds of document or image data (e.g. grey-scale, mapped colour, full colour). - 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: Colour image printing or display applications where the data resource used may depend upon colour handling capabilities of the recipient. - Examples of typical use: To describe recipient capabilities: (& (color=fixed) (color-levels<=6) ) (& (color=grey) (color-levels<=64) ) (& (color=mapped) (color-levels<=240) ) (& (color=full) (color-levels<=16777216) ) Klyne/McIntyre Work-in-progress [Page 26] RFC nnnn Content feature schema for Internet fax 17 November 1998 To describe capabilities used by a document: (& (color=fixed) (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 colour capabilities. - Interoperability considerations: The actual number of colour 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 colour values that it can handle as an inequality (<=), and a data resource declares the number of colours 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-resolution [this document] color-space [this document] color-palette [this document] - Intended usage: Internet fax Colour image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 27] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.4 Colour resolution - Media Feature tag name(s): color-resolution - ASN.1 identifier associated with this feature tag: [[[New assignments by IANA]]] - Summary of the media features indicated: This feature tag indicates a colour resolution capability; i.e. the level of detail to which an individual colour can be specified. Typically, this feature would be used with 'color=mapped', and possibly 'color=grey' or 'color=full', to indicate the number of distinct colours that can be realized. - 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: Colour image printing and display applications where the data resource used may depend upon colour 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=mapped) (color-levels<=240) (color-resolution<=65536) ) (& (color=full) (color-levels<=16777216) (color-resolution<=262144) ) To describe capabilities assumed by a document: (& (color=mapped) (color-levels=200) (color-resolution>=32768) ) (& (color=full) (color-levels=32768) (color-resolution>=32768) ) Klyne/McIntyre Work-in-progress [Page 28] RFC nnnn Content feature schema for Internet fax 17 November 1998 - Related standards or documents: The memo "Media Features for Display, Print, and Fax" [3] defines a feature (color) for indicating basic colour capabilities. - Related feature tags: color [3] color-levels [this document] color-space [this document] color-palette [this document] - Intended usage: Internet fax Colour image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 29] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.5 Colour 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 colour space supported by a device or used by a document. A colour space value provides two types of information: o the representation of a colour value, including the number of colour components o a mapping between colour values and their physical realizations Generic colour space values are provided for applications where the general colour representation used is significant, but exact colour matching is not vital. Specific colour space values are provided for use when exact colour matching is important. - Values appropriate for use with this feature tag: Token Generic colour RGB (generic RGB) spaces: LAB (generic L*a*b*) CMY (generic CMY) CMYK (generic CMYK) Specific colour CIELAB (LAB per T.42 [9]) spaces: (may be extended by further registrations) - The feature tag is intended primarily for use in the following applications, protocols, services, or negotiation mechanisms: Colour image printing and display applications where the data resource used may depend upon colour handling capabilities of the recipient. Scanning applications where the data transferred may depend upon the image generation capabilities of the originator. Klyne/McIntyre Work-in-progress [Page 30] RFC nnnn Content feature schema for Internet fax 17 November 1998 - Examples of typical use: To describe rendering or scanning capabilities: (color-space=[LAB,CIELAB]) To describe capabilities assumed by a document for which approximate colour reproduction is required: (color-space=LAB) To describe capabilities assumed by a document for which exact colour reproduction is required: (color-space=CIELAB) - Related standards or documents: RGB: [[[Reference???]]] LAB: [[[Reference???]]] CMY: [[[Reference???]]] CMYK: [[[Reference???]]] CIELAB: ITU T.42 [9] - Interoperability considerations: When declaring a specific colour space capability for a scanning or rendering device, a corresponding generic capability should also be declared so that feature matching for applications or documents that do not require exact colour matching can be performed. - 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 colour space capability for a device may lead to failure to match colour space for an application or document that does not require an exact colour match. Klyne/McIntyre Work-in-progress [Page 31] RFC nnnn Content feature schema for Internet fax 17 November 1998 - Related feature tags: color [3] color-palette [this document] - Related media types or data formats: TIFF for fax [7] - Intended usage: Internet fax Colour image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 32] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.6 Colour palette - Media Feature tag name(s): color-palette - ASN.1 identifier associated with this feature tag: [[[New assignments by IANA]]] - Summary of the media features indicated: Use with palettized colour (color=mapped), this feature indicates a source of the mapping between pixel values and colour values. When a custom palette is indicated, the palette is carried with the image data. The actual form of the palette data within the image is not indicated by this feature, but is a function of the image file format used. When used with a scanning application, this feature is also associated with a colour discrimination function that determines the region of the colour space that is mapped to each possible pixel value. [[[Lloyd: please check this. I forget the exact terminology appropriate here]]] - Values appropriate for use with this feature tag: Token Custom (contained within image data) ITU-T43 (per T.43 [10]) (may be extended by further registrations) - The feature tag is intended primarily for use in the following applications, protocols, services, or negotiation mechanisms: Colour image printing and display applications where the data resource used may depend upon colour 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-palette=Custom) (color-palette=[Custom,ITU-T43]) Klyne/McIntyre Work-in-progress [Page 33] RFC nnnn Content feature schema for Internet fax 17 November 1998 - Related standards or documents: ITU-T43: ITU T.43 [10] - 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: Specifying an incorrect colour palette value could result in data being rendered in a way that obscures some or all of its content. - Related feature tags: color [3] color-levels [this document] color-resolution [this document] image-file-structure [this document] - Related media types or data formats: TIFF for fax [7] - Intended usage: Internet fax Colour image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 34] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.7 Colour illuminant - Media Feature tag name(s): color-illuminant - ASN.1 identifier associated with this feature tag: [[[New assignments by IANA]]] - Summary of the media features indicated: This feature indicates the source of illuminant information used in interpreting colour values. [[[Lloyd: a few more specifics, please???]]] When a custom illuminant is indicated, the illuminant information is carried with the image data. The actual form of the illuminant information within the image is not indicated by this feature, but is a function of the image file format used. [[[Lloyd: please check this. I forget the exact terminology appropriate here]]] - Values appropriate for use with this feature tag: Token Custom (Contained with image data) CIED50 (per ???) (may be extended by further registrations) - The feature tag is intended primarily for use in the following applications, protocols, services, or negotiation mechanisms: Colour image printing and display applications where the data resource used may depend upon colour 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-illuminant=Custom) (color-illuminant=[Custom,CIED50]) Klyne/McIntyre Work-in-progress [Page 35] RFC nnnn Content feature schema for Internet fax 17 November 1998 - Related standards or documents: CIED50: [[[Reference???]]] - 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: Specifying an incorrect colour palette value could result in data being rendered in a way that obscures some or all of its content. [[[Are these true, or is image rendition relatively insensitive to illuminant???]]] - Related feature tags: color [3] image-file-structure [this document] - Related media types or data formats: TIFF for fax [7] - Intended usage: Internet fax Colour image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 36] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.8 Colour gamut - Media Feature tag name(s): color-gamut - ASN.1 identifier associated with this feature tag: [[[New assignments by IANA]]] - Summary of the media features indicated: This feature indicates a supported range of colour values. Colour values are a sequence of colour components interpreted in the context of some colour space. A colour gamut is indicated by a possible range of values for each of the colour components. For generic gamut matching, suitable tokenized values may be used (e.g. "Video", "Hardcopy"). - Values appropriate for use with this feature tag: String Specific gamut: "lo1..hi1,lo2..hi2, ... ,loN..hiN" Generic gamuts: "Video" [[[reference to be supplied]]] "Hardcopy" [[[reference to be supplied]]] (may be extended by further registrations) - The feature tag is intended primarily for use in the following applications, protocols, services, or negotiation mechanisms: Colour image printing and display applications where the data resource used may depend upon colour 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-gamut=["1..100,-75..75,-75..125","Video"]) Klyne/McIntyre Work-in-progress [Page 37] RFC nnnn Content feature schema for Internet fax 17 November 1998 - Related standards or documents: "Video": [[[Reference to be supplied]]] "Hardcopy": [[[Reference to be supplied]]] - Interoperability considerations: When describing device or document capabilities with a specific gamut, a generic gamut should also be indicated unless very precise colour matching is required. This allows feature matching to be achieved when the exact gamut of a matching device or document is unknown. The number of component-value ranges in a specific gamut string must correspond to the number of components required by the color space used. Colour-intensive applications might choose to understand the content of the specific gamut string and interpret expressions like: (color-gamut<="1..100,-75..75,-75..125") to recognize a match with (say): (color-gamut="20..70,-50..65,-30..100") but this is not a required feature of a generic negotiation framework. - 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] - Related media types or data formats: TIFF for fax [7] Klyne/McIntyre Work-in-progress [Page 38] RFC nnnn Content feature schema for Internet fax 17 November 1998 - Intended usage: Internet fax Colour image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 39] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.9 Colour 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 colour information may be subsampled with respect to luminance data. It is used with continuous colour images (color=full), color spaces that use separate luminance and colour components (e.g. color-space=LAB), and image file structures that support colour subsampling. - Values appropriate for use with this feature tag: String "1:1:1" This value indicates a full set of colour component samples for each luminance component sample. "4:1:1" This value indicates a set of colour 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: Colour image printing and display applications where the data resource used may depend upon colour 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"]) ) Klyne/McIntyre Work-in-progress [Page 40] RFC nnnn Content feature schema for Internet fax 17 November 1998 - Related feature tags: color [3] color-space [this document] image-file-structure [this document] - Related media types or data formats: TIFF for fax [7] - Intended usage: Internet fax Colour image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 41] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.10 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-L TIFF-C 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. - 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. Klyne/McIntyre Work-in-progress [Page 42] RFC nnnn Content feature schema for Internet fax 17 November 1998 In the case of TIFF for fax 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 for fax [7] TIFF V6.0 (Adobe) [[[Reference???]]] - Intended usage: Internet fax Image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 43] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.11 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. - Related standards or documents: MH, MR: ITU T.4 [13] MMR: ITU T.6 [14] JBIG: [[[Reference???]]] JPEG: [[[Reference???]]] Klyne/McIntyre Work-in-progress [Page 44] RFC nnnn Content feature schema for Internet fax 17 November 1998 - 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 for fax [7] - Intended usage: Internet fax Image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 45] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.12 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] Klyne/McIntyre Work-in-progress [Page 46] RFC nnnn Content feature schema for Internet fax 17 November 1998 - 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 for fax [7] - Intended usage: Internet fax Colour image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 47] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.13 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. - 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: [[[Reference???]]] JBIG-T85: ITU T.85 [18] JBIG-T43: ITU T.43 [10] - 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. [[[How is stripe size of a document handled???]]] - Interoperability considerations: To establish the correct conditions for interoperability between systems, capabilities to handle the generic image coding technique and the specific image coding constraints must be established. Klyne/McIntyre Work-in-progress [Page 48] RFC nnnn Content feature schema for Internet fax 17 November 1998 - Related feature tags: image-coding [this document] image-coding-constraint [this document] image-interleave [this document] - Related media types or data formats: TIFF for fax [7] - Intended usage: Internet fax Colour image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 49] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.14 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 (image-coding=???). [[[Lloyd: more detail please???]]] - 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: [[[Need to comment on memory usage???]]] - Related feature tags: image-coding [this document] JBIG-stripe-size [this document] - Related media types or data formats: TIFF for fax [7] Klyne/McIntyre Work-in-progress [Page 50] RFC nnnn Content feature schema for Internet fax 17 November 1998 - Intended usage: Internet fax Colour image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 51] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.15 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. Thus, an entire MRC document is characterized by a set of feature collections --a feature set-- that must be covered by the capabilities of the receiver. 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] Klyne/McIntyre Work-in-progress [Page 52] RFC nnnn Content feature schema for Internet fax 17 November 1998 - 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 for fax [7] - Intended usage: Internet fax Colour image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 53] RFC nnnn Content feature schema for Internet fax 17 November 1998 A.16 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-stripe-size=[0..256]) (MRC-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 for fax [7] Klyne/McIntyre Work-in-progress [Page 54] RFC nnnn Content feature schema for Internet fax 17 November 1998 - Intended usage: Internet fax Colour image scanning/rendering applications - Author/Change controller: IETF (Fax Working Group) Klyne/McIntyre Work-in-progress [Page 55] RFC nnnn Content feature schema for Internet fax 17 November 1998 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=None) (image-coding=MH) (MRC-mode=0) ) (Tiff-F) :- (& (image-file-structure=TIFF-F) (color=None) (image-coding=[MH,MR,MMR]) (MRC-mode=0) ) (TIFF-J) :- (& (image-file-structure=TIFF-J) (color=None) (image-coding=[MH,JBIG-2-LEVEL]) (MRC-mode=0) ) (TIFF-C) :- (& (image-file-structure=TIFF-C) (color=Mapped) (image-coding=[MH,JPEG]) (MRC-mode=0) ) (TIFF-L) :- (& (image-file-structure=TIFF-L) (color=Mapped) (image-coding=[MH,JPEG,JBIG-M-LEVEL]) (MRC-mode=0) ) (TIFF-M) :- (& (image-file-structure=TIFF-M) (color=Mapped) (image-coding=[MH,JPEG]) (MRC-mode>=1) ) 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. Klyne/McIntyre Work-in-progress [Page 56]