Methods and devices for rasterizing transparent pages

摘要

A method for rasterizing transparent pages scans each transparent page twice. The first scanning syntactically interprets a page description file of the transparent page, divides it into page blocks, and writes information of image element objects and transparency parameters into intermediate files. The second scanning reads the image element objects and the transparency parameters from the intermediate files and builds a page bitmap in blocks. A device for rasterizing transparent pages includes interpreting, dividing, file storing and building units. The interpreting unit implements syntactical interpretation. The dividing unit divides pages into transparent and nontransparent page blocks. The building unit implements rasterization according to the transparent or nontransparent page blocks, the information of image element objects and the transparent parameters to build a page bitmap in blocks. The methods and devices herein improve the efficiency of building a page bitmap and decrease memory utilization during generation of the page bitmap.