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

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105294

Allan Haldane <ealloc at gmail.com> changed:

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                 CC|                            |ealloc at gmail.com

--- Comment #4 from Allan Haldane <ealloc at gmail.com> ---
Just to link to the history, this came from bug:
https://bugs.freedesktop.org/show_bug.cgi?id=97612

I tried deleting the line "/Decode [ 1 0 1 0 1 0 1 0 ]" from the pdf, which
that patch added, and confirm that without it the image colors are no longer
inverted.

Here is a stackoverflow discussion of problems with adobe CMYK jpegs, where the
"Decode" fix is suggested: https://graphicdesign.stackexchange.com/a/15906

I haven't yet understood what is going on well. It seems possible to me that
there is some kind of double-inversion going on: Maybe cairo adds the Decode
line to invert the jpegs, but otherwise leaves the metadata alone. Then when
you view that generated pdf again using cairo, it inverts twice: Once because
it detects an adobe jpeg, and again because it finds the new Decode line. I
confirm by looking inside the PDF that the generated PDF still has the "Adobe"
header in the jpeg, and also has an additional Decode line.

Also, for me this is a fairly serious bug which affects about half of the PDFs
I try to print in the last couple months, after I upgraded cairo. For me it
makes evince/poppler effectively unusable for printing pdfs.

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