Re: [xep-support] LZW-compressed TIF files corrupt in PDF output

From: Nikolai Grigoriev (
Date: Thu Mar 18 2004 - 05:25:55 PST

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    > I'm getting skewed images (tiff/LZW) in pdf output
    > (XEP 3.7.4 saved from PhotoShop 7).

    This is because of Photoshop's peculiarity in TIFF
    treatment: it appends an extra zero byte to each TIFF
    strip _before_ LZW compression. We concatenate
    LZW streams without decompression; the extra byte
    introduces a periodic shift and thus makes the image

    > I know this issue was up on the list a while back
    > but I can't seem to find any further discussion on
    > the topic. Is there a workaround?

    The options are as follows:

    1. Set strip size for LZW-compressed images to the maximum,
    so that the whole image stays in a single strip. (I don't know
    if this is a configurable parameter in Photoshop).

    2. Use uncompressed TIFFs. (They will be repackaged
    by XEP using Flate compression, and the resulting PDF
    files will be smaller than with LZW-compressed images).

    3. Re-save your image using some other TIFF generator.
    (These trailing zero bytes in compressed streams are
    a unique feature of Photoshop, not of TIFF format; other
    applications don't necessarily have it).

    4. Use PNG instead of TIFF (alas, not applicable if you need
    CMYK images).

    5. Wait until end of June, 2004, when Unisys LZW patent expires
    in Germany, France, Italy, UK, Japan, and Canada. We will add
    proper support for GIFs and TIFFs within days from that date.

    Best regards,
    Nikolai Grigoriev

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