Merge plane generation for a data processing pipeline

Abstract

A print data processing pipeline for use in a color electrophotographic printer optimizes print quality and minimizes memory usage by separately processing lossy and lossless print data. Lossy print data may include print data for images and lossless print data may include print data for text, line art, and graphics. Partitioning print data into lossy and lossless elements allows application of the print data compression operations optimized for each type of print data. High compression ratios can be achieved on lossy print data by applying visually lossless compression operations designed for the lossy print data. In addition, high compression ratios can be achieved on the lossless print data by applying lossless compression operations designed for the lossless print data. A merge unit combines the lossy and lossless print data streams after decompression to reconstruct the original image using merge data. The merge data is generated in an image processing operation which accounts for the different transparency modes of the page description language print data so that the correct foreground and background placement of objects is maintained. Placement of the color space conversion operation and the halftone operation relative to the merge operation, further optimizes the print quality while minimizing memory usage. The print data processing pipeline includes a direct memory access controller which has the capability to allow print data to be selectively directed to the lossy or lossless compressor/decompressor, the color space converter, or the merge unit.