Patent ID: 8743968

Claim:
A method of analysing image data in an image processor to quantify prior block-based processing of the data, the method comprising the steps of: processing a set of pixel values derived from said image data to generate a spatial difference profile along a line perpendicular to assumed block edges, the spatial difference profile representing differences between values of pixels spaced spatially in a direction parallel to said line; summing the spatial difference profile in a direction perpendicular to said line to form a summation difference profile having values y n where n represents pixel position in units of pixel pitch perpendicular to the direction of summation; measuring inter-maxima distances in said spatial difference profile to a fractional precision in pixel spacing units; and aggregating measured inter-maxima distances to determine a block size; wherein the step of measuring inter-maxima distances in said spatial difference profile comprises the step of using a moment based detector taking at least values y n−2 ; y n−1 ; y n ; y n+1 and y n+2 to detect peaks to a fractional precision in pixel spacing units.