2000.11.29 14:18 "more G4", by Andy
I get some images from a "Life*ODIN" system that are not being read by the libtiff code, nor by other programs, for example Kodak Imaging. This is only some, not all of the files from them. This is using libtiff-3.4beta037.
These images purport to GroupIV TIFF. They are structurally sound TIFF files, but the Group IV data is being illegible. The libtiff decoder is able to get from the single image data strip the upper portion of the data, for example the first couple hundred scan lines, the rest is blank.
There is a "Fax4Decode Warning" emitted, it says "R136711.TIF: Premature EOL at scanline 864 (got 1581, expected 3323)". Then another, "R136711.TIF: Premature EOL at scanline 865 (got 0, expected 3323)". This continues:
scanline 866(got 0, expected 3323)
scanline 867(got 0, expected 3323)
Then there is another warning for each remaining scanline in the image.
The images have two private tags, 34645 (0x8755) and 34646 (0x8756)
So, I go to Fax codec and see where this is emitted, to see if I can get it to skip the special case and extract the bulk of the image data. So I go to tif_fax3.c. This warning is kicked off by the function Fax3BadLength. Fax3BadLength is defined into the badlength macro. I define FAX3_DEBUG and recompile. Now it is providing considerably more verbose output as it decompresses.
On a separate note, can anyone say what softwares use the page numbering system, that is to do with TIFFTAG_PAGENUMBER?
company Apex Internet Software