I know that lossy normally lessens the image quality in the compression process, but Curtail has two options:
Lossless mode: Compresses the file by removing unnecesary data that does not affect image quality; thus reducing file size. Lossy mode: Compresses the file much further by lowering the visual quality of the image; thus reducing the file size but looking a bit worse.
After using the lossless mode, I’ve personally done very thorough image comparisons to see if there was any discernible difference between the original file and the compressed file. I could not find any visual difference.
In Curtails own words on their site “It supports both lossless and lossy compression modes with an option to whether keep or not metadata of images.”
Okay, thanks. I guess it’s not possible at the moment then.