Re: [pdf-devel] Bug in LZW filter?

[Georg Gottleuber]

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Hi,

On 27.10.2011 11:59, Juan Pedro Bolívar Puente wrote:
> Do you have also test cases that fail without the changes and succeed
> otherwise?

Take any LZW encoded PDF stream bigger 1K. It will fail decoding without
my changes.

As mentioned in my email from 2011-09-20:
> I tested with 11 different LZW-Streams from 8
> different PDFs:
> With my fixes all 11 LZW-Streams are decoded well (without: none)
> With my fixes all 3 Ghostscript Streams are encoded to the same bytes
> (without: none)

My setup for testing the decoder (Earlychange = 1; default):
(example PDF: http://www.kripsy.de/texte/sp/rs_sit_kripsy.pdf)

Extract encoded LZW-Stream
$ pdfshow -e -b  rs_sit_kripsy.pdf 3 > lzwstream

Decode with GNU PDF
$ ./pdf-filter -i lzwstream -o lzwdecoded.gnupdf --lzwdec --lzw-earlychange

Decode with
$ pdfshow -b rs_sit_kripsy.pdf 3 > lzwdecoded.mupdf

Compare both outputs:
$ vbindiff lzwdecoded.gnupdf lzwdecoded.mupdf

Regards,
Georg

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