A method as well as a system, a device, an encoding apparatus, a decoding apparatus, a module and a computer software product for image processing is disclosed. The image comprises a pixel matrix, in which the pixels comprise a first number of bits. The pixel matrix is divided to two or more blocks of pixels. The pixels are processed on a block-by-block basis to form encoded pixel values including a certain second number of bits. Bit strings are formed on the basis of the encoded pixels. When decoding the image the bit strings are examined to find out the encoding method used in encoding the pixel, and decoding is performed on a block-by-block basis to retrieve pixel values of the image.