A pixel counts as different only if it's outside the range of the other
image's 3x3 neighborhood (widened by a tolerance) and enough of its neighbors
are too, so edges a pixel off, filtering rounding and speckle drop out.
8x8 block averages catch broad shifts separately, and heatmaps show where.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
