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Формат JPG |
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JPEG file format documents -------------------------- The official standard for JPEG image compression is not available on-line. To get it, you have to order a paper copy from ANSI; it's not cheap. (As of May 1992, Part 1 is $95 and Part 2 is $47, plus 7% shipping/handling.) Ordering information is attached below. If you are not in the USA, you should try your national ISO member organization first. The JPEG standard does NOT define a concrete image file format, only a family of compression algorithms. The Independent JPEG Group recommends that one of these two file formats be used for JPEG-compressed images: JFIF: for simple applications that just need the image data; TIFF 6.0: for more complex applications that need to store extra data about an image, such as color correction curves. JFIF is a simple, restrictive, but easily processed format. TIFF 6.0 is a complex format that will let you represent almost anything you could want, but it is less portable than JFIF since different applications tend to implement different subsets of TIFF. These formats are defined by the following documents: jfif.ps.Z JFIF 1.02 specification (in PostScript format) TIFF6.ps.Z TIFF 6.0 specification (in PostScript format) jfif.ps.Z is available in this archive (ftp.uu.net: graphics/jpeg). TIFF6.ps.Z is available by anonymous FTP from sgi.com (192.48.153.1), file graphics/tiff/TIFF6.ps.Z. Each of these documents assumes you have the JPEG standard, but is otherwise self-contained. It should be noted that the TIFF 6.0 spec of 3-June-92 has a number of serious problems in its JPEG features. A clarification note will probably be needed to ensure that TIFF JPEG files are compatible across different implementations. The IJG does not intend to support TIFF 6.0 until these problems are resolved. -------------------------------------------------------- Date: Mon, 14 Oct 91 09:41:36 PDT Subject: How to order official JPEG documents From: Greg Wallace A. Phases in ISO Standards Development In the ISO standards creation process, there are 4 levels of documents. The first is the Working Draft (WD), a purely informal document. When the ISO Working Group (WG) which prepares the WD feels it is ready, it becomes a Committee Draft (CD). The CD is the first form of the ISO document which is officially examined and balloted within ISO, outside of the WG which created it. When the voting member nations are happy with the technical content and general exposition of a CD, it is promoted to Draft International Standard (DIS). The DIS is then balloted not only among the voting member nations, but among other branches of ISO and among other committees as well. Generally, this phase of voting puts less emphasis on scrutinizing the technical content, and more emphasis on proper form and "positioning" with respect to other standards efforts. Approval of a DIS ballot results in publication of the International Standard (IS). B. JPEG Status The "JPEG committee" is an ISO WG, the full formal nomenclature being ISO/IEC JTC1/SC2/WG10, hereafter WG10 for short. (Incidentally, a new Sub-Committee (SC) in ISO is forming; the JPEG WG is expected to join this new SC29, and become JTC1/SC29/WGxx in November 1991). At its August 1991 meeting, WG10 examined the ballot results of CD Part 1 (the votes were almost unanimously positive), made several editorial revisions to the CD per the ballot comments, and concluded that the revised CD deserved promotion to DIS. The DIS Part 1 should be published late November or December, at which time its ballot will begin. If the ballot results are positive, the IS should be published by Spring 1992. Note that Part 1 is essentially the JPEG specification, including many guidelines for implementation, and Part 2 is Compliance Testing. WG10 has a goal of agreeing on the details of Compliance Testing at its November 18-22 meeting. If successful, CD Part 2 should be published by January 1992. Note also that the ISO version of the JPEG standard will be common text for an identical standard within CCITT. In parallel with the publication of the ISO DIS Part 1 will be publication of CCITT Draft Recommendation T.81 (Part 1). C. Document Ordering Information (1) To obtain the JPEG Committee Draft Part 1: Call ANSI Sales at (212) 642-4900, and ask to order the following document. To ensure the clerk is certain which document you want, give all three of the following (redundant) document designations: (a) The JPEG Committee Draft Part 1, entitled: ``Digital Compression and Coding of Continuous-tone Still Images, Part 1: Requirements and guidelines'' (b) Number: ISO/IEC CD 10918-1 (c) Alternate Number: SC2 N2215 (2) To obtain the JPEG Draft International Standard Part 1: Call ANSI Sales around the end of November, and ask if the DIS version of the above is available yet. Use the ordering information above, but replace CD with DIS in (a) and (b). The alternate number (c) was not known at the time of this writing. (3) To obtain the JPEG Committee Draft Part 2: Call ANSI Sales around the end of December 1991, and ask if the following document is available yet: (a) The JPEG Committee Draft Part 2, entitled: ``Digital Compression and Coding of Continuous-tone Still Images, Part 2: Compliance testing'' (b) Number: ISO/IEC CD 10918-2 (c) Alternate Number: not known at time of this writing. |
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09.08.2009
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Инженер и веб-мастер Богданов Андрей Александрович
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