Modifying a Page During Spooling
You can develop a printing extension to make device-independent changes to image data during the spooling phase of printing. QuickDraw GX sends a message to the extension just before each page in a document is spooled to disk. Your printing extension can take this opportunity to make any changes to the page that it wishes. The changes are then incorporated into the final version of the page that is saved in the spool file.For example, you might develop an encryption printing extension that is used during spooling to encode the printing data as it is spooled to disk and decode it as it is read
for printing. This extension allows security-conscious organizations to print sensitive documents and ensure that they are secure during the time they reside in spooler files.
It also allows the spooled files to be distributed over a network with confidence that the contents are hidden during transmission time.
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