Fixes issue 11393.

The problem is that left and top make no sense for a width by height array; they only make sense in a larger array where from which a smaller part is extracted.  Thus, the overall size of the array is provided to CopyRegion in addition to the sub-region.  EncodeXFB already handles the extraction, so CopyRegion's only use there is to resize the image (and thus no sub-region is provided).