A method and apparatus are disclosed for providing an indication of a level of distortion created by blocking artifacts in an image comprising a plurality of pixels, the method comprising for each pixel in a first given direction, determining a corresponding gradient between the pixel and a neighboring pixel, for each pixel in the first direction, summing each of the corresponding determined gradient in a second direction to provide a plurality of gradient summing values, computing a level of distortion for each of at least one potential block size using at least one of the gradient summing values, determining an actual block size using the computed at least one level of distortion and providing the level of distortion corresponding to the determined actual block size.