1999.05.31 20:35 "Re: Bug in LZW decoding", by Niclas Borlin
I've decoded some large LZW files with version 3.4 beta 37 and have been having problems with the corrupted data. These files are bilevel (1 bit per pixel) and 65542 pixels by 57596 pixels.
Interestingly, an older version of tifflib (3.3) decodes these files fine. Has any one experienced anything similar?
I've had some weird results with the same tifflib version and images with:
Compression: LZW or Zip (deflate)
Predictor: Horizontal differencing
Samples per pixel: 1
Bits per samples: 16
Endianess: Other (i.e. big-endian images on little-endian arch. and v.v.)
The bug appears to be related to the predictor. I think one byte-swapping too many was performed. Can't remember the source location where I think I located the bug, however. :-(
Do your images match my compression/predictor/endianess? If so, I suggest you debug the decoder looking for this bug.
Niclas Borlin email: Niclas.Borlin@cs.umu.se
Department of Computing Science phone: (+46) 90-786 68 32
Umea University fax: (+46) 90-786 61 26
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