Minimum Variance Partitioning Crash

[TheAllTinker]

Hi - I've been using Minimum Variance Partitioning for colour palette reduction; most of the time it works perfectly fine, however I've run into odd cases where the code crashes. It may be perhaps related to the distribution of colours in the image, but I'm only guessing. It does seem more common with lower-resolution/downsampled source material (e.g. 64x64) - the crash is perfectly repeatable given the same input.

Tracing the code through the debugger, it appears that the node partition threshold hasn't been initialised by the time of the first SplitPartition() call - i.e. node.partition->threshold on line 256 in minimum_variance_partitioning.cpp is 0xCDCDCDCDCDCDCDCD. Just as a test I added zero-initialisation to KDTree::Partition, but this didn't help, it just crashed further on in ComputeSumProjections.

For me it crashes every time with the following image:

And the following code:

dip::Image dipImage(imageBytes, dip::UnsignedArray{64, 64}, 3);
dipImage.SetColorSpace("RGB");
dip::Histogram hist(dipImage, {}, {dip::Histogram::Configuration(0.0, 255.0, 64)});
dip::Image tmp;
dip::CoordinateArray centers = dip::MinimumVariancePartitioning(hist.GetImage(), tmp, 256);

Where imageBytes is just the image bytes as loaded by my own code from PNG.

[crisluengo]

Thanks for reporting this!
I very much appreciate the minimal reproducible example, it made it really easy to reproduce the issue.

This has been fixed in a900d36.

[TheAllTinker]

Thanks very much for the quick fix! =) Working perfectly now.