How does XnView handle this? Is it possible to implement this? Especially for smaller changes like red eye reduction it would be very useful not to recompress the whole file.However, the JPEG images consist of a number of independently encoded blocks typically 8x8, 8x16 or 16x16 pixels in size, and there is a way to treat these blocks individually without having to recompress the untouched ones. Better JPEG takes advantage of this possibility allowing for partial image editing without total recompression (red eye removal, data/text imprinting, copy/paste, etc.).
2. Another question: Is it possible to read the compression ratio of a jpeg file and suggest this ratio for the save or save as dialog?
3. Is it possible to add lossless a border around a jpeg? This should work like crop the other way round. Just increase the canvas size by multiples of 8 pixel without recompressing the whole picture.
Just some suggestions, perhaps it is even impossible.