2003.11.19 00:40 "[Tiff] TIFF: predictor question", by Chris Losinger

i'm noticing something really strange in my app. for testing speed, i'm saving an image, reading it back, then saving again and that reading back, in a loop.

i've notice that if i use the predictor when saving ( TIFFSetField(tiff, TIFFTAG_PREDICTOR, 2); ), the image is degraded *each time* it goes through the loop. the first time through, the image read back looks fine. the second time, the degradation starts (and it looks exactly as if what i'm seeing at is the output of the predictor - the basic image is still there but the colors are all wrong and there is banding around features). it gets worse each time i read and save the same image, and by the 10th time through, the image is pure noise. i'm using LZW and Deflate, for testing.

if i don't turn the predictor on, there are no problems.

does this sound right?

-c