What Is a Perceptual Hash?
A perceptual hash condenses an image into a short fingerprint that reflects how the image looks rather than its exact bytes. Two visually similar images produce hashes that differ by only a few bits, so the distance between hashes measures similarity. This makes it useful for matching images that have been resized, recompressed, or lightly edited.
Why it matters
Byte-for-byte comparison reports a difference for trivial recompression. A perceptual hash tolerates that noise, so visual tests and deduplication flag genuinely different images instead of harmless encoding changes.
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