Here is another clue that might help someone find the bug:
The shift in data is independent of the number of channels in the deep-data part. When I tested with 6 channels (named A, B, G, R, X, and Y), the channels are written and read in that (alphabetic) order. Looking at the bad data read for pix[0] I
discovered that pix[0].A was garbage, but pix[0].B was pix[256].A. Each channel of pix[0] was the previous channel's value for the last sample. It looks like the data were in the buffer, but the start pointer was off by one float.
On 04/20/2018 02:50 PM, Richard Hadsell wrote:
Your last suggestion was most helpful. I had already examined the pointers and
strides, set the part to NO_COMPRESSION, and generated only 1 sample per pixel,
but I had not tried it with tiny images.
I found that an image with a single scanline and up to 256 pixels was okay. However, 257 pixels resulted in the first pixel (pix[0]) having junk and the other pixels being shifted, so that pix[1-256] had the values that should have been in pix[0-255].
This was the result from reading the file.
Using 'od' to look at the file showed that the last float in the file was,
indeed, the sample for pix[256]. Maybe the write was okay, but the read was
not.
(Testing with 258 pixels in the scanline resulted in bad data for pix[0-1], and
values in pix[2-257] were the samples that should have been in pix[0-255].)
For the test with 257 pixels, I looked at the data in TotalView and saw that readPtr, as calculated in line 673 of ImfDeepScanLineInputFile.cpp, points to floats that correspond to the samples that are bad. The first float is junk, and the next 256
samples are those that should have been in pix[0-255]. The float after that was 0, not the value that should have been in pix[256], so I conclude that the data in the buffer were not read correctly from the file.
Of course, I don't know enough about the layout of data in the file to know
whether the problem is in reading or writing. I can see that the samples are
there in the file, but maybe they are in the wrong place.
I hope this is enough information for someone to duplicate the problem. I
don't think I can take it any farther myself.
--
Dick Hadsell 203-992-6320 Fax: 203-992-6001
Reply-to: hads...@blueskystudios.com
Blue Sky Studios http://www.blueskystudios.com
1 American Lane, Greenwich, CT 06831-2560
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