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November 2000
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2000.11.21 16:09 "YCbCr Subsampling 1,1 problems", by Joe Grassi
I'm wondering if anyone has had success viewing raw, subsampled 1,1 Ycc tiff images. I have been using the rgb2ycbcr program to create some tiff ycc files which are 1,1 subsampled, and are not JPEG compressed. When I try to look at them, these images crash my viewers. The default subsampling of h =2, and v=2 works okay, as I have no problems viewing those output images. owever, when I try using rgb2ycbcr -h 1 -v1, I find that I cannot view my images. I am using the ImageMagick Display tool as well as The Gimp in a linux environment. In both cases the viewers give a segmentation fault on my Ycc images that have Subsampling 1,1. I am able to use this subsampling if I also JPEG compress the image. In that case the viewers work fine. I've gone through the tiff list archive over the last year looking for a similar problem. I found reference to Bug #10, and made the change (x = w instead of x = w>>1 in file tif_getimage.c) and rebuilt, but this did not solve my problem. Can anyone tell me if this is a problem with the viewers, or with the rgb2ycbcr code? The Gimp seems to have some problems even with subsampled 2,2 Ycc tiff files as it says it "fell back to RGBA, image may be inverted". It does indeed invert the image, is this a known Gimp problem? Thanks, Joe