An image processing apparatus comprising a supply unit configured to supply image data one piece of pixel data at a time, and an encoding unit configured to encode the image data supplied by the supply unit, the encoding unit selecting, as prediction pixel data, locally decoded data of one pixel out of n pixels (n is an integer greater than or equal to 2) that were encoded immediately before a pixel to be encoded and have been locally decoded, and encoding a difference between the prediction pixel data and data of the pixel to be encoded, wherein the supply unit supplies pixel data to the encoding unit in a predetermined order according to which all of the n pixels are pixels that are adjacent to the pixel to be encoded.