🚀 go-pugleaf

Re <9204160601.AA05559@raisin-nut>
<1992Apr16.051955.23318@msc.cornell.edu>:

> Most color postscript output has 
> the rgb color definitions embedded within it, right?

I don't understand what this question means.  There is no definition
or standard for "color PostScript output."  Some file formats (e.g.,
PCX) use a colormap; some (e.g., PPM) use RGB values directly.

> So why does pstoppm.ps define and use its own colormaps?

pstoppm.ps uses a colormap only for 8-bit output, where it is
unavoidable.

> ppm24run even seems to use the default X colormap.

ppm24run does not use a colormap: it outputs 24-bit values containing
8 bits each of unmapped R, G, and B.

> Is there a newer version of pstoppm.ps that addresses this 
> problem, i.e. that uses the colors defined in the
> postscript file?

pstoppm.ps always respects the colors defined in the PostScript file.
The question is how it represents them in the output:

	- ppm1run produces black-and-white output, so there is no issue.

	- ppm24run uses 8-bit-per-component true color as mentioned above.

	- ppm8run uses a colormap.

The output of ppm8run is actually a questionable use of the PPM
format.  As I understand it, the format includes PBM (1 bit per
pixel, black and white), PGM (N bits per pixel, gray levels), and PPM
(3*N bits per pixel, true color), so 8 bits with a colormap is not
really covered.

The person who wrote the original version of pstoppm used an X
colormap, but there is no particular reason for this.  If you really
want 8-bit, color-mapped output, you can change the color map
(palette) in pstoppm easily enough: the format is documented under
the makeimagedevice operator in language.doc.

L. Peter Deutsch :: Aladdin Enterprises :: P.O. box 60264, Palo Alto, CA 94306
ghost@aladdin.com, ...decwrl!aladdin!ghost ; 415-322-0103 8-9 AM M-F/msg
	    "Implementation is the sincerest form of flattery."