Compression-Related Noise

Another kind of unwelcome pattern commonly found in images is a pattern generated by the application of lossy compression, of which JPEG is the most common. Lossy compression averages pixel values through interpolation. This interpolation process creates repeating patterns of averaged pixel values in JPEG images. This interpolation pattern results in both loss of image data and the posterization (creation of areas of similar-value pixels). The higher the degree of compression, the more severe the imposed pattern appears. Most digital cameras by default capture images by using at least a moderate degree of JPEG compression to allow users to store more images on their removable media. Higher-quality images will be created if this compression is avoided in the first place. However, if you receive images that have JPEG-related posterization patterns, you should remove them.