[cairo-bugs] [Bug 105294] pdftocairo -pdf inverts image color in this PDF

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Fri Jun 15 17:12:02 UTC 2018


--- Comment #10 from Allan Haldane <ealloc at gmail.com> ---
I looked at the cairo/poppler/libjpeg code and I think I see why the "adobe"
tag has no effect.

In poppler in DCTStream.cc in init(), it chooses the colorXform as follows: If
the adobe header is present it uses the transform specified in the header,
which for these jpegs is the CMYK transform. If the header is *not* present and
there are 4 color components (as in these jpegs) also use the CMYK transform.
So for our jpeg the CMYK transform is used whether or not the adobe header is
present. After that point, the adobe header seems to be ignored, and poppler
treats adobe-CMYK and non-adobe-CMYK identically.

So possibly there is a poppler bug involved here. It seems like poppler inverts
all CMYK images.

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