Introducing Pxsum!

Have you ever wanted a quick and easy way to evaluate the visual equality of images — i.e. their pixels — independent of complicating factors like format and encoding?

Whether you're looking for proof of losslessness or want to clean up an old wp-content/uploads directory with ten thousand copies of the same logo, our new x86-64 Linux CLI tool pxsum can help!

Pxsum works just like traditional checksum tools like md5sum and b3sum, but rather than hashing files directly, it reads and decodes each image into a neutral RGBA bitmap format, then hashes the resulting pixel byte stream.

Under the hood, it uses the modern BLAKE3 hashing algorithm, ensuring fast and collision-safe results.

All of the "popular" image formats — and JPEG 2K/XL, haha — are supported:

AVIF
BMP
GIF
ICO
JPEG
JPEG 2000
JPEG XL
PNG
TIFF
WebP

Crunching

The interface mirrors those of other checksum tools like md5sum, so should be immediately familiar to the target audience.

# STDIN to STDOUT.
cat image.jpeg | pxsum

# Source path(s) specified as arguments.
pxsum image.jpeg another.png

# Crunch an entire directory.
find ~/Pictures -type f -exec pxsum {} +

The output looks like you'd expect:

fc6e48e935f7b7330cb6bc95c8c725f57e8d9b1efe01b7afc90ea53e9d968aa9  ./assets/ash.jpg
84372180f4763895ff1165487003106774953ad6bce56b5b1344893c52f175c2  ./assets/carl.jpg
2212ead939f81398e078745cbdfeb57f67398c6d3ff16f822449df035bafee0f  ./assets/cmyk.JPG
3c112bc262d2f292adec259c35ad1981088e9cd45ccc5669ada0c9b7efe08559  ./assets/dingo.png

Alternatively, you can group the results by checksum using the -g/--group-by-checksum flag:

2212ead939f81398e078745cbdfeb57f67398c6d3ff16f822449df035bafee0f
  ./assets/cmyk.JPG
2ac10da49b973cd4c44bd3b15cf4e0882f3bfd9bd0edf99bca28b3376ff1a70f
  ./assets/santo.bmp
  ./assets/santo.ico
  ./assets/symto.bmp
3c112bc262d2f292adec259c35ad1981088e9cd45ccc5669ada0c9b7efe08559
  ./assets/dingo.png

The grouped output can, for example, make it easier to identify duplicate images, but if that's your use case, use the --only-dupes flag as that will additionally filter out any one-offs:

2ac10da49b973cd4c44bd3b15cf4e0882f3bfd9bd0edf99bca28b3376ff1a70f
  ./assets/santo.bmp
  ./assets/santo.ico
  ./assets/symto.bmp

Either way, you can save the results to a file the usual way:

pxsum -d ~/Pictures > pictures.chk

Verification

Previously-generated results can be fed back into the program to check that nothing's changed. Just set the -c/--check flag:

# These are all equivalent.
cat pictures.chk | pxsum -c
cat pictures.chk | pxsum -c - # The STDIN dash is optional.
pxsum -c pictures.chk
pxsum pictures.chk -c         # The order doesn't matter.

This output also looks just the way you'd expect:

./assets/ash.jpg: OK
./assets/dingo.png: OK
./assets/cmyk.JPG: OK
./assets/carl.jpg: FAILED

Interested?

As with everything we do, pxsum is licensed WTFPL. You can use and abuse it freely.

For more information, sources, and build/install instructions, visit the Github repo.