Bluebonnet Studios

Lightroom Plugins

Find Similar Photos

The photographs you already have twice

Private release Version 2.0.0 · Plugin · macOS

Finds the photographs you already have twice — the burst frames, the re-export at a different size, the re-edit — by comparing what the images look like rather than the bytes they contain, and gathers each group into a collection.

What it does

Select photographs in the Library and run Library > Plug-in Extras > Find Similar photos (histograms). Enter a similarity threshold — 0.7 to 0.9 suits most catalogs, and 1.0 finds near-exact duplicates — and each group of similar photographs is placed in its own collection inside a Similars collection set. Files in a format the comparison cannot read are listed first, and you decide whether to continue without them.

Every pair of photographs inside a group meets the threshold. Two pictures are not grouped just because each resembles a third one in a different way, which is how similarity grouping usually drifts into nonsense on a large selection.

Similar, not identical

Instead of

Matching checksums and calling it duplicate detection. A checksum finds byte-identical files, which is the easy half of the problem and rarely the half you have. Two exports at different sizes, a re-edit, the same frame from a burst — none of those match on bytes, and all of them are what you actually want grouped. Comparing colour histograms, then rejecting pairs whose coarse structure does not agree, finds them without grouping every photograph that merely shares a colour cast.

What it changes

Collections, and nothing else. It never writes photo metadata and never modifies an image file. Running it again offers to replace the previous Similars set.

Status, stated plainly

The comparison runs in a native helper bundled inside the plugin, built from C++ against OpenCV, libheif and LibRaw, because pixel comparison across a large selection is not work for Lightroom’s scripting runtime. That helper is currently built for Apple Silicon Macs only, and it still loads part of its image-library stack from Homebrew at run time: it works on a Mac with Homebrew’s opencv, libheif and libraw installed, and is expected to fail on one without them.

Tested in Lightroom Classic on a Mac. The progress bar is an estimate, and cancelling does not stop a comparison already under way.

Licensing

The plugin’s own code is licensed under Apache 2.0. For HEIC and RAW support it bundles libheif and libde265, which are LGPL, LibRaw, which is LGPL or CDDL, and the x265 encoder, which is GPL 2.0. The GPL is not compatible with Apache 2.0 for redistribution as one combined work, and each bundled library keeps its own licence in any copy you receive.

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