PostScript level 2 and PostScript 3 support several compression algorithms. This means that pages can contain compressed images when being send to the RIP and that the RIP will handle decompression. Among the compression formats support are CCITT group 4 and JPEG. A PostScript error that refers to DCTdecodefilter points to the RIP having problems decompressing an image.
JPEG compressed images
- A corrupted JPEG image can lead to PostScript errors when trying to print the document that contains the image. The error message may even specifically point to a problem with an ‘Unknown or invalid JPEG marker’. To find the corrupted image, remove images from the layout until the file does print. Then try to open the image and resave it (using a different compression setting).
- One of my customers reported occasional ‘DCTdecodefilter’ PostScript errors when imaging the yellow plate of large (100 MB and up) JPEG compressed images on an Agfa RIP running PSE 11. Resending only that color always solved the problem. Resaving the files uncompressed may also be a good work-around.
OPI DCS-merging
Some OPI-systems can’t handle DCS JPEG-compressed images properly. When a queue is setup to do a DCS-merge, the OPI-system will not merge properly and a PostScript error offending command ‘DCTdecodefilter’ pops up on the RIP.