Internet File Formats/InternetFileFormatsCD.bin/graphics/tiff/unix/archive.z/archive/text0093.txt

Text File | 1995-09-20 | 1.6 KB | 39 lines

    To:  [e-mail]
    Subject:  Integrating TIFF extension
    Date: Mon, 23 Jan 1995 17:18:47 PST
    From:  Adam Rybicki <[e-mail]>

    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.)

    1. 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).

    2. 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.

    3. 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.

    Sam