CompressJPEG callback

This page applies to Harlequin v13.1r0 and later; both Harlequin Core and Harlequin MultiRIP.

This procedure is called whenever the filter operator is invoked for the DCTDecode filter. While it is reasonable to assume that the data to be read from the resulting channel is image data, the call is not necessarily directly associated with a call to image or colorimage. No arguments are included on the operand stack for this callback.