glonlas/uniqueimages

uniqueImages is a command-line tool that finds duplicate photos in a folder, even when they've been altered. If you have two copies of the same picture but one has been resized, brightened, or had its colors shifted, the tool can still tell they're the same image and flag them for you. It only works with JPG files and currently can't catch cropped or mirrored versions. The tool works in two passes. First, it does the obvious check: it looks for files that are byte-for-byte identical, which catches exact copies quickly. Then, for everything that's left, it does something cleverer. It generates a "perceptual hash" for each image, basically a fingerprint that captures what the picture looks like rather than the raw file data. Images with similar fingerprints get grouped together as near-duplicates. This is useful for anyone sitting on a large, messy photo collection. Imagine you've been on a trip, downloaded photos from multiple cameras and phones, and ended up with the same shots saved at different sizes and quality levels scattered across subfolders. Running this tool would surface those groups of matching images so you can pick the best version and delete the rest. One tradeoff worth noting: because it relies on a perceptual hash algorithm from 2006, it has real blind spots. Cropped or mirrored versions of a photo will slip through undetected, and the tool is limited to JPGs only. The README doesn't go into detail on performance with very large collections, but the two-pass approach, quick exact-match check first, then the slower perceptual comparison, is a sensible way to keep things efficient.