Photo CD Demo 1/Demo.bin/formats/jpeg/jpeg.ptr

Text File | 1980-02-04 | 6KB | 130 lines

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 specification (in PostScript format)
TIFF6.ps.Z    TIFF 6.0 specification (in PostScript format)

jfif.ps.Z is available in this archive.  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.


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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 [phone], 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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