Patent ID: 7940996

Claim:
A method, comprising: processing an image in a first dimension and a second dimension, the image including a series of M blocks of pixels in the first dimension and a series of N blocks of pixels in the second dimension forming M columns of blocks of pixels and N rows of blocks of pixels respectively, where M and N are whole non-zero numbers, each row and/or column of blocks of pixels including a series of pairs of blocks of pixels each including adjacent first and second blocks of pixels, the second block of pixels in a preceding pair of blocks corresponding to the first block of pixels in a next pair of blocks, the processing including the following steps for at least a part of the pairs of blocks of pixels of at least a part of said rows and/or columns of blocks of pixels in said image: /a/ determining an indication of a block boundary between the respective first and second blocks of pixels in said pair of blocks of pixels, /b/ deciding, based on said indication of a block boundary whether the block boundary is a visible block boundary or an invisible block boundary, and /c/ repeating steps /a/ and /b/ for a next pair of blocks of pixels, wherein, if at least one invisible block boundary is present between two visible block boundaries, it is decided that a uniform distortion zone is detected in the image, with the visible block boundary or boundaries and the uniform distortion zone or zones indicating an image quality level.