Method of identifying relevant areas in digital images, method of encoding digital images, and encoder system

A digital image encoder system for encoding image data corresponding to input images comprising:

• an encoder module arranged to process input images using compression values,
• a receiving module arranged to receive information representative of pixels in a first digital image,
• a group value module arranged to calculate a sum, a mean, or a median of said information for groups of neighboring pixels in said first image to form a group value for each group of pixels,
• a difference calculation module arranged to calculate differences between group values,
• a comparing module arranged to compare said differences to a predetermined threshold value,
• an identification module arranged to identify a group of pixels as being in a relevant area if said difference is equal to or above said threshold value, and to identify said group of pixels as being in a not relevant area if said difference is below said threshold value, and
• a compression value setting module arranged to set a compression value (QP) for each group of pixels based on the identification of relevant areas, such that groups of pixels in relevant areas are given a first compression value, and groups of pixels in not relevant areas are given a second compression value, said second compression value being representative of a compression giving a lower image quality than the first compression value.