There is provided a method for processing a variable length code encoded image having a plurality of scan lines, wherein each scan line has a number of original code blocks including a differentially encoded parameter. The method includes defining a subarea of the image having parts of a number of the scan lines, extracting the subarea, generating a set of auxiliary code blocks having an auxiliary differentially encoded parameter based on the first differentially encoded parameter of a first code block of a first current scan line in the subarea, and associating the auxiliary code blocks with the subarea. There is also provided an apparatus and a computer program product thereof.