What Is a Pixel Diff?
A pixel diff compares two images point by point and reports which pixels differ, usually producing both a count and a highlighted overlay. A configurable threshold lets small color deltas from anti-aliasing be treated as equal. The result drives a pass or fail decision in visual regression testing.
Why it matters
A raw pixel count is the most precise signal of visual change, but without a tolerance it is too sensitive. Tuning the threshold balances catching real regressions against ignoring sub-pixel rendering differences.
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