Compare same-sized images by pixel threshold, with explicit transparency compositing, a change mask and red overlay.
Your input
Outputs are cleared when the input changes.
Result
Enter your data or use the example, then run the tool.
Worked example
The two 2 × 2 samples differ at one pixel. Threshold 0 gives 1 changed pixel out of 4, or 25%. Comparing the same sample with itself gives 0%.
Method
After browser orientation and decoding, composite each RGBA pixel onto the same chosen RGB background. Count pixels whose maximum absolute channel difference exceeds the threshold. The mask is red on transparent; the overlay highlights changes over the first composited image.
Limits
Images must have identical oriented dimensions; no scaling or registration. At most 10 million pixels per image and 20 MiB per file; static JPEG/PNG/WebP. Browser color conversion may affect results. This is not perceptual similarity, structural comparison or evidence of tampering.
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