1995.01.24 18:29 "Re: Integrating TIFF extension", by Sam Leffler
I have been trying to integrate YCbCr TIFF support into my project by using libtiff and I ran into some inconsistencies between the spec and libtiff (this may be the fault of my erroneous interpretation of the spec, in which case I need to be corrected.)
- According to the spec, BitsPerSample (quoting from memory) is supposed to be an array sized by the sample count to allow different number of bits per sample (e.g. R,G,B = 5,6,5 bits respectively.) Libtiff always treats BitsPerSample as a single quantity. Is libtiff somehow "normalizing" the BitsPerSample to the greatest element of that array?
The library does not support multi-sampled images where the bits/sample vary. This is documented several places such as intro(3T).
- YCbCr files cannot be read by scanlines, but reading by strips works as expected. However, in libtiff there is no way to specify which particular sample to load if PlanarConfiguration is 2. Or is there? Tile-based YCbCr files should work, but I have no files in that format.
If PlanarConfig is 2 (separate planes) then individual samples are in different strips/tiles; to get a particular sample you read the appropriate strip/tile.
- Has anyone integrated JPEG support by using jpeglib?
It's coming, but is not yet ready for distribution. When it's ready there will be a posting to this mailing list.