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[Openexr-devel] Y RY BY images

From: Jim Hourihan
Subject: [Openexr-devel] Y RY BY images
Date: Wed, 14 Mar 2007 15:25:12 -0700

Hi all,

Is there a trick to writing Y RY BY images? I've tried a number of things and I cannot for the life of me understand what's going on. I've been able to reduce the problem to the following:

I can successfully write out a scanline piz 3 channel R G B image with no sub-sampling. By declaring the channels as Y RY BY instead of R G B (all other things being the same), the Imf library will create a file that exrheader indicates should be kosher, but exrdisplay will not read. exrdisplay produces this error:

"X and/or y subsampling factors of "BY" channel of input file "out.exr" are not compatible with the frame buffer's subsampling factors."

exheader says this:

file format version: 2, flags 0x0
channels (type chlist):
    BY, 16-bit floating-point, sampling 1 1
    RY, 16-bit floating-point, sampling 1 1
    Y, 16-bit floating-point, sampling 1 1
compression (type compression): piz
dataWindow (type box2i): (0 0) - (609 405)
displayWindow (type box2i): (0 0) - (609 405)
lineOrder (type lineOrder): increasing y
pixelAspectRatio (type float): 1
screenWindowCenter (type v2f): (0 0)
screenWindowWidth (type float): 1

This is the case with no sub-sampling indicated (sub-sampling 1) for both the Channel struct and the Slice. Somehow the Imf library is treating the image differently because of the channel names. I've been using the example image Rec709.exr to generate the input. (I would like to match my output to Rec709_YC.exr eventually).

I tried to update my CVS tree, but it looks like savannah is down. My last checkout was a couple of weeks ago. (using 1.5)


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