Note that the horizontal dimension ofģ6 is 4 multiples of the MCU width ( 8) plus an extra Let's take the following 36x28 JPEG image. Unfortunately, this is a problem that many users of digicams will encounter when they try to rotate their images losslessly. So, for the purposes of the discussion below, you should treat the required image dimensions as 16 pixels where it reads 8 pixels. For these photos, the tiles (MCUs) can be treated as being 16x8 or 16x16 pixels respectively. Many digital cameras use chroma subsampling to reduce file size at the expense of losing color information (generally 2x1 or 2x2 chrominance subsampling). NOTE: For the following discussion, I am describing images that have been compressed without chroma subsampling. MCU size will be termed an odd-sized image. See my article on the JPEG Minimum Coded Unit (MCU).įor the purposes of the following discussion, images whose dimensions are not a multiple of the JPEG images are constructed with 8x8 tilesįor the background on how an image is represented by the 8x8 tiles, please

How to flip a jpeg image