Abstract: Skew angle in a document image is estimated using operators known from mathematical morphology. Skew angle in a document image (A) is estimated by run-length smoothing the image and then producing a plurality of eroded run-length-smoothed images. The run-length-smoothed image (RLSA(A)) is eroded using a linear structuring element (k2L?) oriented at each of a plurality of different angles (?). The angle of the linear structuring element which produces an eroded image having the greatest surface area is designated as the skew angle. A plurality of run-length-smoothed images (RLSA?(A)) may be produced, each generated by smoothing the document image using a linear structuring element (k1L?) oriented at a respective different angle (?i). Then each run-length smoothed image (RLSA?(A)) is eroded using a linear structuring element oriented at the corresponding angle (?i).

Abstract: Table-like structures in documents are located by analysis of sub-regions (crops) on the document. The analysis involves determining the location of lines having lengths above a certain threshold and assigning these lines to groups. A set of adjacent lines is assigned to a common group if the separation between adjacent pairs of lines within the set is less than a threshold value. The crop selected as the location of the table-like structure is that having a group with the greatest number of lines. When the technique is applied to locating title blocks in technical drawings, it is preferred to analyze crops corresponding to the corners or ends of the document. The analysis is also applicable to an image of the document produced at a reduced resolution.

Abstract: The invention relates to a method and an apparatus for processing image data stored on a memory for rendering an image on a device. The method comprises dividing the image data into a number of portions of image data, each portion consisting of a number of untruncated data lines; applying to each portion of image data a rasterizing algorithm comprising: a. writing the portion of image data to a RAM, b. halftoning said portion of image data for obtaining a portion of rasterized image data, and c. writing the portion of rasterized image data to a mass memory; assembling the portions of rasterized image data on the mass memory for obtaining rasterized image data; dividing the rasterized image data into a number of blocks; and applying a transformation algorithm to each block of rasterized image data for obtaining blocks of processed image data.