YCCK JPEG from a PDF with wrong colors about twelvemonkeys

[Schmidor]

Thank you. I think that solves our problem with the PDF.
There are many "interesting" variations in PDF writers 😄

[haraldk]

Curious...

Thanks for the sample and report! I'll investigate why we get different colors than libJPEG...

[haraldk]

Okay... This sample file has an APP14/Adobe marker specifying YCCK, however the "Adobe" string is followed by a 0x01 "Start of Header" character instead of the normal NULL-termination 0x00... So we don't really see it as an Adobe marker but an "Adobe\0x01" custom marker that we ignore...

We could probably change the identifier parsing to stop at the first ASCII control character (<= 0x20) instead of the NULL only. But I'm not sure the sample file is strictly correct...

[haraldk]

...or maybe I'm just wrong in assuming that every JPEG marker identifier string should be 0-terminated...

Supporting the DCT Filters in PostScript Level 2 in section 18 Adobe Application-Specific JPEG Marker actually specifies only the characters 'A', 'd', 'o', 'b' and 'e' followed by a two byte version... While I have always thought the version was only a single byte.. 😮

If this is indeed correct, then I guess I need to rewrite a lot of the JPEG marker parsing. 😛

[haraldk]

Hmm.. Thinking about it some more, I think (the authors of) the encoder that wrote the file actually just misread the spec. My guess is that they tried to write an App14/Adobe marker with version 1.00, but encoded it as 0x0100 (256) instead of the correct 0x0064 (100)... I think the most recent version is either 1.01 or 1.02, there really isn't any 2.56 version around...

Anyway, I should still handle this, as the spec says two byte version, and not 0-termination...