Compression level: Since compression is not lossy, the only reason to use a compression level less than 9 would be a too long time to compress file on a slow computer. Nothing to fear from decompression: it is as quick whatever the compression level.
GIMP suggests using compression for lossless .png images, "compressed" images are saved using the same file type. If I set
compression level to
0 when saving the image is several times larger than the original image. How does "lossless compression" work and do I lose quality by using it?