IFX Mail Archive: RE: IFX> New version of PDF/is (PDFax) spe

IFX Mail Archive: RE: IFX> New version of PDF/is (PDFax) spe

RE: IFX> New version of PDF/is (PDFax) specification is now available.

From: Rick Seeler (rseeler@adobe.com)
Date: Wed Nov 20 2002 - 11:33:13 EST

  • Next message: Rick Seeler: "RE: IFX> New version of PDF/is (PDFax) specification is now available."

    My comments below...

    -Rick

    > -----Original Message-----
    > From: Buckley, Robert R [mailto:RBuckley@crt.xerox.com]
    > Sent: Tuesday, November 19, 2002 9:32 PM
    > To: 'Rick Seeler'
    > Cc: Buckley, Robert R
    > Subject: RE: IFX> New version of PDF/is (PDFax) specification
    > is now available.
    > Importance: High
    >
    >
    > Rick,
    >
    > I don't understand the prohibition on banding, although I
    > don't have my PDF manual handy to know what's in Sec. 2.1.2.
    >
    Here's the link to the PDF Reference so you can check out section 2.1.2:
    http://partners.adobe.com/asn/developer/acrosdk/docs/filefmtspecs/PDFRef
    erence.pdf

    Specifically, it says:
    "A page's content stream contains operands and operators describing a
    sequence of
    graphics objects. A PDF viewer application maintains an implicit current
    page
    that accumulates the marks made by the painting operators. Initially,
    the current
    page is completely blank. For each graphics object encountered in the
    content
    stream, the viewer places marks on the current page, which replace or
    combine
    with any previous marks they may overlay. Once the page has been
    completely
    composed, the accumulated marks are rendered on the output medium and
    the
    current page is cleared to blank again."

    I was advised by our chief PDF scientist, Ed Taft, that creating bands
    in this way violates the imaging model and would be highly
    controversial. There is also concern that images that are broken down
    this way may show "banding" artifacts due to dithering.

    BTW - This, in no way, restricts the use of JBIG2 Striping which is part
    of the JBIG2 format itself.

    If it's a big enough concern, I can raise this as a technical issue with
    the 'PDFLang' committee.

    > One of the arrangements I can foresee is splitting a page
    > into stripes or tiles, which break the page into a sequence
    > of non-overlapping Image XObjects. The exact arrangement is a
    > function of the writer--no particular reader behavior is mandated.
    >
    > Is something like this permitted? Table 4-1 suggests it is.

    As for how this banding/striping would be done, I have come up with
    this...
    In the 'Content Stream', the Creator would insert a Marked Content (DP)
    operator to indicate that all of the previous image objects do not
    overlap any of the remaining objects on the page:

    (The following illustrates a two band page (bands running
    horizontally))...
    100 0 0 500 25 25 cm <-- 100 units high, 500 units wide, 25 units in
    from the top and left edges.
    /Im1 Do <--- Display the first band
    /Fis_BandY <<>> DP <--- New 'Banding' indicator.
    100 0 0 500 25 125 cm <-- Next band region. 100 high, 500 wide, 25
    from the left, 125 from the top.
    /Im2 Do
    ...
    Notice the new keyword '/Fis_BandY'. There would also be a keyword
    '/Fis_BandX' for banding in the other direction.

    >
    > I didn't see a mechanism for identifying a possibly private
    > subprofile of the standard profiles you define here. Is there
    > such a way to do this?

    Yes, you would add a new keyword to the 'PDF/is' object, like this:

    /PDFis [28 1 ...]
    /XRX_MyPrivateKeyword <-- Your new keyword. It can also have
    parameters, if you wish.
    /Root ...

    Your company should register with Adobe's name registration at:
    http://partners.adobe.com/asn/developer/acrosdk/pdfprefix/register.jsp
    This will make sure your name does not conflict with anyone else's.
    It's generally a good idea to put an '_' at the end of your prefix. In
    that case, you're limited to three characters (like "XRX_"). Once you
    have the prefix, you can go nuts making new keywords as long as they all
    begin with the prefix.

    >
    > Overall, nice job. I expect our team will get back to you
    > with some detailed comments.

    Thanks.

    >
    > Rob
    >
    > -----Original Message-----
    > From: Rick Seeler [mailto:rseeler@adobe.com]
    > Sent: Tuesday, November 19, 2002 4:50 PM
    > To: ifx@pwg.org
    > Subject: IFX> New version of PDF/is (PDFax) specification is
    > now available.
    >
    >
    > I have just released revision 0.3 (Proposal - Working Draft)
    > of the PDF/is specification (formerly "PDFax"). The new
    > version is available here
    > "ftp://ftp.pwg.org/pub/pwg/QUALDOCS/pwg-> ifx-pdfis-latest.pdf"
    > and on the web site.
    >
    > Major changes
    > for this release:
    > - Format name changed to "PDF/is" from "PDFax". 'IS' stands
    > for 'Image-Streamable'.
    > - All new PDF name extension keywords are now registered with
    > the Adobe PDF Name Registry as 'Class 2' names to avoid conflicts.
    > - 'Banding' of images on a page was rejected as this concept
    > violates the Adobe Imaging Model (See [pdf] Section 2.1.2).
    > - Format was modified to be compliant with PDF/X-3 specification.
    > - 'cm' operator calculations were incorrect and incomplete.
    > These are now fixed.
    > - Calculation to determine image resolution is now part of
    > specification.
    > - Profile letters and numbers have now been replaced with
    > readable strings to aid in comprehension.
    > - Various minor document cleanup.
    >
    > A new version of IPPFAX will be coming soon.
    >
    >
    > -Rick
    >



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