| 摘要 |
PROBLEM TO BE SOLVED: To quicken printing processing which includes the conversion of print data in a host computer or data transmission with a printing device. SOLUTION: Previous image data, whose printing is requested, are stored in a storing means as cache data, and the cache data are inquired by a confirming means according to the next printing request, and the presence or the absence of the same document in the storage cache data is confirmed (S1). When the absence of any cache data is confirmed (No), normal processing is executed (S2). When the presence of the cache data is confirmed (Yes), the changing points for print data and the cache data are confirmed by a difference- detecting means (S3). An image data preparation command, stored at the time of the previous print data caching, is compared with an image data preparation command converted from the print data whose printing has been requested, and the difference (changing point) is detected and returned to a PDLpreparing part. When the presence of change is confirmed in the processing S3 (Yes), difference image data (PDL data) are prepared from the image data preparation command by the PDL preparing part, and replaced with the pertinent part of the cache data (S4). The image data whose changing point is replaced are transmitted to a printing device (S5). When the absence of change is confirmed in the processing S3 (No), the pertinent cache data are transmitted to the printing device (S6) and outputted, so that the cache data can be printed at a high speed.
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