Photoshop: Problem parsing TIFF files [that are too big]

From: Isaac Kohn (ikohn@UIC.EDU)
Date: Wed Dec 12 2001 - 01:59:30 CST

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    Message-Id: <200112120810.fBC8ACo08615@sitelicense.arizona.edu>
Date:         Wed, 12 Dec 2001 01:59:30 -0600
From: Isaac Kohn <mailto:ikohn@UIC.EDU>
Subject:      Photoshop: Problem parsing TIFF files [that are too big]
To: mailto:IMAGELIB@LISTSERV.ARIZONA.EDU

    <pre> Hi all,

    I was searching the web for information about a problem I've encountered, and I came across this list. It seems that there was a discussion related to my problem in Oct 1998, but the issue was never resolved. I thought perhaps someone could enlighten me.

    I'm dealing with a program that generates a handful of TIFF files. Unfortunately I didn't write the program and I don't have access to the source code. In any case, it seems that the TIFF's it produces are readable by Photoshop (5.5) only until they exceed a certain size.

    Example: I have here two TIFFs that have almost identical headers. One is 85 x 105 pixels, and the other is 85 x 43810 pixels. I don't know much about the TIFF spec, but... here are the relevant snippets of the header tags:

    ImageWidth: 85 ImageLength: 105 BitsPerSample: 0x00c8 (??? 24-bit should give 0x0018) StripOffsets: 300 SamplesPerPixel: 3 RowsPerStrip: 105 StripByteCounts: 26775 (ie 85 x 105 x 3) filesize is 80,625 (ie 3 x StripByteCounts + StripOffsets)

    ImageWidth: 85 ImageLength: 43810 BitsPerSample: 0x00c8 StripOffsets: 300 SamplesPerPixel: 3 RowsPerStrip: 43810 StripByteCounts: 11171550 (85 x 43810 x 3) filesize is 11171850 (ie StripByteCounts + StripOffsets)

    Note that the StripByteCounts tag in the larger image seems to be calculated exactly as in the smaller image, yet the filesize does not bear the same relationship to the StripByteCounts value. It's almost as if the larger image only has 8 bits of color data per sample, as opposed to the smaller image, which clearly has 24 bits (ie 3 bytes) per sample.

    No problems with the small image, but on attempting to open the large one, Photoshop spits out "Could not open the document because of a problem parsing the TIFF file." Interestingly enough, even the large TIFF is perfectly readable in Microsoft's "Imaging for Windows" applet, but no matter what I do (resave, etc), I can't get the mailto:$*@#$! image to open in Photoshop.

    If anyone knows the technical details of TIFF formatting or has any useful advice at all, I would appreciate it very much.

    Thanks in advance.
    --Isaac K.

    </pre>

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