Patent ID: 8744204

Claim:
A method for the detection of a block raster in an image which has a plurality of pixels, to each of which at least one pixel value is assigned and which are adjacent to one another along horizontal and vertical pixel boundaries (x j , x j +1) the method comprising: a) establishing a first raster having raster boundaries (x j +dx j ), which run either parallel to the vertical pixel boundaries or parallel to the horizontal pixel boundaries, and the position of which is specified by an offset (OF) and a spacing (SP) between them; b) ascertaining a raster dimension that is a function of edge dimensions of at least some of the raster boundaries (x j +dx j ); determining of an edge dimension on a raster boundary that lies between two pixel boundaries comprising the following steps b1) ascertaining an edge dimension of a first pixel boundary which is next to the raster boundary using a high-pass filtering in a direction perpendicular to the first pixel boundary; b2) ascertaining an edge dimension of a second pixel boundary which is located next to the raster boundary using a high-pass filtering in a direction perpendicular to the second pixel boundary; b3) weighting the edge dimensions of the first and second pixel boundaries as a function of the spacing between the raster boundary and the first pixel boundary and the second pixel boundary; c) repeating the method steps a) and b) for a second raster; d) selecting one of the first and second rasters taking into account the ascertained edge dimensions thereof.