Anti-aliasing of raster images using assumed boundary lines
AssigneeInternational Business Machines Corporation
InventorWilliam M. Doumas
Life of this patent
Estimating the term…
Abstract
A method for improving the quality of raster imaging in which an array of pels is selected having a pattern of filled and unfilled pel positions. In the selected array, an assumed line is determined based on its pel pattern by comparing the pel pattern of the selected array with respect to a plurality of predetermined pel patterns each having a predetermined associated line and angle. When a match is found, the assumed line of the selected array is determined as the associated line of the matched predetermined array. The intensity of the pel at the center of array is selected in accordance with the angle of the line. The line, at the predetermined angle, is positioned to bisect the pel to be enhanced. Intensity is determined by the relative areas of the portions of the bisected pel.
Claims18
A method for improving the quality of raster imaging in which the image is represented by a plurality of selected square arrays of filled pels forming a filled pel area and unfilled pels forming an unfilled pel area, each square array having an edge between the filled pel area and the unfilled pel area and containing at least nine pels, comprising the steps of:
- (a) establishing a 0.degree. set of arrays having at least the top row compeltely unfilled and in which a 0.degree. line is formed by an edge of the filled pel area which is parallel to a horizontal line of the array,
- (b) establishing a 45.degree. set of arrays in which a 45.degree. line is formed by the edge of the filled pel area parallel to a diagonal of each array,
- (c) establishing for a first intermediate set of arrays at least one line having a predetermined angle intermediate between said 0.degree. and said 45.degree. lines and having a top unfilled row and a bottom filled row and an intermediate row having at least the same number of filled pels from row to row downwardly,
- (d) transposing the first intermediate set and its associated line about a vertical line and rotating the transposed first intermediate set 90.degree. to provide a second intermediate set of arrays each having an associated line intermediate between said 45.degree. line and the vertical line of the array,
- (e) rotating the (1)0.degree., (2)45.degree., (3) first intermediate, and (4) second intermediate sets of arrays and the associated lines of each set in a sequence of 90.degree. rotations to provide respectively (1) sets of arrays having associated lines of 90.degree., 180.degree., and 270.degree. with respect to the horizontal, (2) sets of arrays having associated lines of 135.degree., 225.degree., and 315.degree. with respect to the horizontal, (3) third intermediate and (4) fourth intermediate sets of arrays each having associated lines,
- (f) selecting square arrays representing the image, each selected array having an odd number of pels,
- (g) comparing each selected array with the sets of arrays to seek a match of a selected array with a particular set, and
- (h) determining a pel intensity for the center pel of each selected array having a match in accordance with the angle of the line associated with the matched set.
In a method for a visual display of graphic pel patterns representated by arrays of foreground and background pels, the improvements including the steps of:
- (a) first establishing predetermined relationships between pel patterns and respective associated assumed lines wherein the associated assumed line of a pel pattern is substantially similar to a boundary line between foreground and background pels within the pel pattern;
- (b) second establishing a predetermined relationship between each assumed line and an associated pel intensity;
- (c) selecting a square array having a pel pattern of foreground and background pels such that both foreground and background pels occur in said selected array;
- (d) comparing the pel pattern of the selected array with the pel patterns having associated assumed lines;
- (e) determining a match between the pel pattern of the selected array and one of the pel patterns having an associated assumed line thereby establishing an assumed line for the selected array only in response to the match;
- (f) selecting the pel intensity associated with the established assumed line;
- (g) modifying the intensity of a pel within the selected array in response to the selected pel intensity;
- and
- (h) generating pels with said foreground, background and modified intensities.
Dependencies are inferred from the claim text.