10.2.3. Color Printing in Ghostscript

10.2.3. Color Printing in Ghostscript

Ghostscript's default color dithering is optimized for low-resolution devices. It will dither rather coarsely in an attempt to produce 60ppi output (not dpi, ppi - the "apparent" color pixels per inch you get after dithering). This produces rather poor output on modern color printers; inkjets with photo paper, in particular, are capable of much finer ppi settings.

To adjust this, use the Ghostscript option-dDITHERPPI=x, where x is the value to use. This may or may not have an effect with all drivers; many newer drivers (the Epson Stylusstp driver, for example) implement their own dithering and pay no attention to this setting. Some drivers can use either the regular Ghostscript or driver-specific dithering (the Canon Bubblejet bjc600 driver, for example).

Ghostscript's dithering is in fact rather rudimentary. Many things needed for good output on modern printers are simply not available in the Ghostscript core. Various projects to fix this situation—and the free software world does have the software to do so ready and waiting—are hampered by Ghostscript's licensing situation and the resulting "cathedral" development style. Beginning at the Open Source Printing Summit 2000, however, all the necessary people are talking, so you can expect this situation to improve shortly.