Method and apparatus for smoothing an expanded bitmap for two-state

Abstract

A method for smoothing expanded bitmap data is provided for use in laser printers or computers that use two-state, two-dimensional image data created by word processors, computer-aided drafting systems, and the like. The method would typically be utilized within a laser printer at its common graphics engine, just after the input source data has been rasterized. The source bitmap data having low-resolution pels is first divided into higher resolution pels, and the appearance of its diagonal lines would otherwise have a jagged appearance if such data is not smoothed. Once the expansion factor is determined, the present method takes pel data in word-sized portions and performs (in an Outer Loop) various logical operations upon these words of data to smooth adjacent rows of the higher-resolution pels. Each pair of words of pels is evaluated through a series of logical operations in an Inner Loop, before indexing to the next group of pels in the same row and starting a new Outer Loop. Once the end of the line has been reached, the method automatically seeks data from two rows of pels at a Y-axis position that is one step lower with respect to the low-resolution pels from the source data file. The same logical operations are again performed on each pair of words of pels until the entire line has been smoothed. These operations continue until the entire bitmap has been smoothed, and the logical operations occur very quickly so as to not slow down the overall operation of the laser printer.