Patent ID: 7920741

Claim:
A computer-implemented method, comprising: performing by one or more computers: generating an initial histogram for a rectangular region of an input image, wherein generating the initial histogram comprises merging two or more column histograms, each corresponding to a column of pixels having a height equal to a height of the region and comprising a plurality of bucket values, each bucket value being dependent on values of pixels in the column; wherein all pixels in the region are represented in one of the columns of pixels corresponding to the two or more column histograms; performing a filtering operation over the region by operating on values in the initial histogram to produce a result value, associated with the region, for a pixel of a second image; generating a second histogram for a second region of the input image on a same horizontal scan line of the image as the region and overlapping the region by at least one column of pixels, wherein said generating the second histogram comprises computing a new column histogram for each column of pixels included in the second region but not in the region and merging bucket values of the new column histograms with corresponding bucket values of the initial histogram; wherein each new column histogram comprises a plurality of bucket values, each bucket value being dependent on values of pixels in the column; performing the filtering operation over the second region by operating on values in the second histogram to produce a second result value, associated with the second region, for a second pixel of the second image; and rendering the second image dependent on the first and second result values.