[cups.development] The best way to get a raster for printer with 3 levels per pixel?

[Michael Sweet]

You should dither the output - see Gutenprint, the CUPS book examples, or the CUPS DDK driver library (which includes multi-level dithering code you can use) for inspiration.

Relying on 2-bit-per-color support from the RIP filters is not safe anyways - only Ghostscript and the imagetoraster filter actually support that path, and we're officially deprecating anything besides 1, 8, and 16-bits per color in CUPS 1.5.

On Aug 13, 2010, at 9:57 AM, Paul Newall wrote:

> It seems my (kodak ESP) printer can make 2 dot sizes. So it can produce dots for each colour that are: white ,small, or large. It has 3 levels per pixel per colour.
> The data to be sent to the printer has 2 bits per pixel per colour. 00=white, 01=small dot, 10=large dot. If you send 11 you get white.
> So I am using a raster with 2 bits per colour, which will have 4 levels 00,01,10,11 and mapping the result to get 3 levels, so 00=00, 01=01 small dot, 10=01 small dot, 11=10 large dot.
> This is not very linear so I don't know if it gives the best result. Does anyone know of any better ways to produce the 3 level output?
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________________________________________________________________________
Michael Sweet, Senior Printing System Engineer, PWG Chair