Unik for Mac
Getting rid of duplicate images can be a tedious work although the process is highly recommended: duplicates take up unnecessary space that can be used better, but also clutter your albums.
Unik is a small Mac app that can prove to be your best friend in this situation: drag and drop the folders or iPhoto albums you want to clean up and Unik will identify the files that need to be removed.
The Unik comparison algorithm does not analyze the binary data but the actual image content. This way, the app is able to find the photos that share the same content regardless of the image position (will find even the ones that are rotated or flipped), resolution or color saturation (works with gray scaled images).
However, Unik also includes a second comparison method: metadata. In the Options panel you can decide which one better suits your needs and then you get to adjust the similarity threshold. The same area allows you to exclude the photos that have a low contrast level.
For your convenience, Unik allows you automatically select images from the results list that match certain criteria (the file / folder name contains a certain string, the latest / earliest / largest / smallest or lowest / highest resolution among its group, ) and then quickly remove them. The filters can be applied to the current selection or to the complete results list.
You can decide quite easily if the selected files are the ones you want to delete because Unik displays thumbnails for each detected image group. To reduce the processing time, the app also caches the results so you will be able to access them faster at a later time.
All in all, Unik is a great tool if you are looking for a way to quickly identify duplicate images by comparing the image content or the associated metadata.