[gs-bugs] [Bug 692235] Rendering PDF to 8bit colors shows bad colors in display device

bugzilla-daemon at ghostscript.com bugzilla-daemon at ghostscript.com
Sun Jul 24 16:55:55 UTC 2011


Robin Watts <robin.watts at artifex.com> changed:

           What    |Removed                     |Added
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |
            Summary|Rendering PDF to 8bit       |Rendering PDF to 8bit
                   |colors shows bad colors     |colors shows bad colors in
                   |                            |display device

--- Comment #24 from Robin Watts <robin.watts at artifex.com> 2011-07-24 16:55:52 UTC ---
After some more discussion with Russell, I've pulled the previous patch,
reopened this bug, and updated the title slightly to reflect that it's only the
display device that is affected.

The commit reverting the patch is 961a9a9.

Why have I reverted the patch?

Well, firstly, it tests out OK for me, it gave Russell problems (he got just
greyscale in colorcir.ps).

Secondly, it will break any code (such as GSview) that expects the standard 8
bit palette.

Thirdly, a vanishingly small number of people will be using 8 bit output in the
display device.

Having done the work on the patch however, it has caused me to question the
original bug report; the complaint was that gs was unsuitable for producing 8
bit color output images, say for use as thumbnails. This is NOT the case, as
you would presumably be using the png256 or similar devices, rather than the
display device to achieve such things.

Those devices use the 6x6x6 color cube rather than the 96 color palette that
the display device does, and so will produce much nicer results.

A better question might be "why does the display device use a non-standard 8
bit palette", and the answer would be "historical reasons".

Martin, as the original bug reporter, can you comment please. Why do you
specifically need the display device to work in 8 bits? (Clearly it would be
nice if it worked better than it did, but is it actually essential for you?)

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