Method and apparatus for saving printer memory

摘要

A page printer uses alternative internal representations for the print data in each of multiple lateral strips that make up the page. Page description language input is converted to an intermediate display list format that is sorted into display commands associated with each strip. If during input the display list representation of the data fills the memory allotted to its storage, one or more of the strips is converted from display list format to raster format and compressed using a lossless compression algorithm. If storage of compressed strips subsequently exceeds available memory, raster data is further compressed using a lossy compression algorithm. Additional display list commands are rasterized by decompressing the compressed strips, processing the new commands and recompressing the data using lossless or lossy compression as required. If the display list does not overflow memory during input, the complete strips are rasterized and compressed one at a time in the order in which they will be printed. The rasterizing time is stored. Should memory overflow at any point in the process, then the rasterizing times for the remaining strips are determined without storing the raster output. A decision can then be made for each strip to rasterize it to the print engine on the fly, pre-compute and store it as lossless compressed raster data, or revert to a lossy-compressed pre-computed version.