LibTiff Mailing List
TIFF and LibTiff Mailing List Archive
January 2004
Previous Thread
Next Thread
Previous by Thread
Next by Thread
Previous by Date
Next by Date
Contact
The TIFF Mailing List Homepage
This list is run by Frank Warmerdam
Archive maintained by AWare Systems
Thread
2004.01.14 12:01 "COLORMAP and byte padding", by Stephan Assmus
Hello, I'm adding write support to the libtiff based OpenBeOS TIFF Translator. I want to support palette images. The format of the colormap that TIFFSetField(tif, TIFFTAG_COLORMAP, ???); expects is unclear to me. In the documentation, it just says Tag Name Count Type Notes TIFFTAG_COLORMAP 3 uint16* 1<<BitsPerSample arrays Ok, so there are 256 entries in the palette if I have 8 bits per sample. So much I follow, but what's with the uint16* ?!? And why Count == 3? The BeOS colormap bitmaps all use the same system wide palette, which consists of 256 entries each representing an rgb color with 3 (4 actually) 8 bit values for r, g, b (and alpha). Am I supposed to fit a 24 bit RGB value into 16 bits and have 256 uint16s? Or do I have 3 * 256 uint16s with 16 bits for each r, g and b? I have also a couple more questions about strip size and byte padding. There seem to be two alternating fields that determine strip size: TIFFTAG_ROWSPERSTRIP rows per strip of data TIFFTAG_STRIPBYTECOUNTS bytes counts for strips Can both be used at the same time to tell libtiff that strip byte counts != rows per strip * samples per pixel * width ? (So that there are some padding bytes at the end of each row...) Best regards, -Stephan