Importance

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Abstract

Digital input commands defined in a page description language are separated in two types of instructions: first instructions resulting in solid regions on the printed output and second instructions resulting in halftoned regions. The first instructions generate a binary bitmap indicating a high or low density of the solid regions and a binary bitmask indicating whether recorder elements belong to a solid or screened region. The bitmap and bitmask are preferentially compressed by a lossless compression method. The second type of instructions generate a contone map, representing images having contone levels and graphics having intermediate levels. The contone map is preferentially compressed by a lossy compression method, stored on a storage medium and retrieved once the output device must render the rasterized image. The rasterized image is constructed on the fly from the compressed bitmap, bitmask and contone map, which is halftoned before combination with the bitmap. A serious amount of memory can be saved, while keeping up with the speed of the rendering process in the output devise and without deteriorating the quality of the reproduction.

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First Claim