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Created an attachment (id=645) [details] test case Versions tested: 4.0.3 & 4.0.6 via x86-64 Linux distros, 3.9.5 (32-bit) & 4.0.6 from source under Linux and 4.0.5 on OS X while double checking the test cases. TIFFReadScanline() produces what appears to be the correct output. It also agrees with ffmpeg-N-78600-g7ad6a21 and ImageMagick-6.7.7-10 output. Test cases based on the sample code within the tiff manual attached. Related bug [1]. $ tar -xzf test_case.tar.gz $ cd test_case $ make $ mkdir output $ for t in test_case_rgbaimage test_case_rgbaimage2 test_case_scanline; do \ ./$t old_logo.tiff > output/$t.pam; done $ cmp -b output/test_case_rgbaimage.pam output/test_case_rgbaimage2.pam $ cmp -b output/test_case_rgbaimage.pam output/test_case_scanline.pam output/test_case_rgbaimage.pam output/test_case_scanline.pam differ: byte 68, line 8 is 4 ^D 17 ^O [1] https://bugs.chromium.org/p/webp/issues/detail?id=292
Created an attachment (id=646) [details] image diff Output from: $ compare output/test_case_rgbaimage.pam output/test_case_scanline.pam
I forgot to mention that I was seeing 'Connection refused' when trying to cvs login so I wasn't able to test the latest code.
tiffinfo test_case/old_logo.tiff shows that the alpha channel of this file is a unassociated alpha channel (ie the R,G,B components are not premultiplied with the alpha value). The TIFFRGBA API then goes in the putRGBUAcontig8bittile() function that do the multiplication of the R,G,B components by the alpha value. This seems to be done on purpose The only related entry I can find in the changelog is the following one, but apparently that behaviour must be even older: {{{ 2006-04-11 Joris Van Damme <joris.at.lebbeke@skynet.be> * libtiff/tif_getimage.c: Revision of all RGB(A) put routines - Conversion of unassociated alpha to associated alpha now done with more performant LUT, and calculation more correct - Conversion of 16bit data to 8bit data now done with more performant LUT, and calculation more correct - Bugfix of handling of 16bit RGB with unassociated alpha }}} So probably this is mostly a documentation issue
Bugzilla is no longer used for tracking libtiff issues. Remaining open tickets, such as this one, have been migrated to the libtiff GitLab instance at https://gitlab.com/libtiff/libtiff/issues . The migrated tickets have their summary prefixed with [BZ#XXXX] where XXXX is the initial Bugzilla issue number.
