RawTherapee
RawTherapee deals with image editing and conversion of photos clicked in RAW format. This software supports almost all kinds of DSLR images and has the ability to process multiple RAW files, which may be in 16 to 32-bit formats and other basic image formats like JPEG, PNG etc. This application also offers a rich toolset for image editing, especially for color correction, noise reduction, rotation, exposure and shadow correction, changing picture tone to vignette and other filters, data image post-processing, framing, white balance, etc. Raw Therapee uses multi-threaded algorithms which can be performed only on powerful PCs. If the app is not running on a relatively powerful PC, then they may enjoy only a few benefits. This app utilizes system resources in the best ways possible, making use of every last bit of processing power on your system.
Why you must get it: 
This application allows the users to edit images in a single program rather than using multiple windows. It has an integrated file manager which allows the user to view, sort, filter, and mark multiple images and lets them bookmark these files on the OS too. Rawtherapee allows users to have complete access over their images that are meant to be edited. Additionally, it allows the users to add frames, retouch images after editing, and create collages.