Metrics not working properly for certain image sizes

[iebert]

I have encountered two problems:

1. If the first dimension of an image (the height) is < 64, then all metrics will return -100 all the time. SSIM will even fail. Oddly that does not seem to be a restriction for the 2nd dimension. For an example, an image of size (64,10) will work fine, but an image of (62,64) will return -100 for all metrics (and SSIM fails).

2. I used an image of size (96,55) and all metrics gave me a dominating checkerboard pattern. I imagine this might come from 55 being odd.