2012.07.13 23:28 "[Tiff] Combinations of Predictor flags (Horizontal) with other TIFF tags", by Ryan Wong

Dear TIFF maintainers,

Recently I encountered a TIFF image with LZW compression, Photometric Palette, and Horizontal Predictor. This image got trapped in a Tiff tag cleanup tool, which stripped off the Predictor tag and rendered the result illegible. I would like to know if there is documentation or first-hand accounts of valid/invalid combinations of this Predictor flag with various other Tiff tags.

For example:

  * What colorspaces (photometric interpretation) is it compatible with? Does LibTIFF handle these combinations correctly?  * Is it valid for TIFF JPEG? If so, does it apply to the RGB values or the YCbCr values?  * The TIFF 6.0 documentation's description makes it sound like it is applicable to BitsPerSample less than 8 (in particular it describes a way to apply horizontal prediction to 1, 2 and 4 bits per samples.) Does anyone have a valid sample image of this? (not crafted with hex editor)  * If case 2 exists, has anyone seen it with one of the bitonal Fax formats e.g. TIFF_CCITT_FAX ?

First-hand accounts will be very useful because they represent the tag as is used in the world, not from some theoretical technologists in a draft committee. (My apologies to committee members who also had Engineer's licenses.) Thank you for your insights.Ryan Wong