image-deduplication-tool is a script designed to scan specified paths and calculate the DCT hashes of all the images there. It compares the hashes to find closest-looking image pairs, despite various alternations (such as crop, rotation, gamma/color correction, noise, etc.), optionally presenting them in a feh image viewer for the operator to easily compare and remove one of the versions. It uses libpHash to produce and compare perceptual hashes.
Attic is a deduplicating backup program. The main goal of attic is to provide an efficient and secure way to back up data. The data deduplication technique used makes Attic suitable for daily backups since only actual changes are stored. Main features: space efficient storage, optional data encryption, and off-site backups.