Re: [ gnuplot-Bugs-1575425 ] "with image" ignores gamma for postscript output (fwd)

[Daniel J S. <dan...@ie...>]

Petr Mikulik wrote:
>>On Wednesday 11 October 2006 10:07 am, Petr Mikulik wrote:
>>
>>>I have just filled in the enclosed bug (announced to me by another
>>>gnuplot user) ... could someone figure out an appropriate "filter"
>>>for the postscript "image" operator so that the gamma correction
>>>works also for "with image" as it works for "with pm3d"?
>>
>>Shouldn't the gamma be a per-image correction rather than something
>>to do with the current palette?
> 
> 
> Yes, it is; palette is updated (changed, written to ps file, ...) before 
> each plot
> 
> 
>>I would have thought that the gamma correction belongs in the routine that 
>>reads in the data. That makes it terminal-independent.
> 
> 
> No, it is for displaying, as all "set palette" properties. There, postscript 
> is the only terminal that avoids calling cb2color because it implements this 
> function by postscript primitives, so it should do it for "palette gray 
> gamma" as well.

Well, this may be the reason that PostScript looks different to me.  On your treminals please try the following and look at all the output:

set palette gray gamma 1.5
test palette
set term png
set output 'foo.png'
test palette
set output
set term postscript eps
set output 'foo.eps'
test palette
set output

I see that the PostScript gamma implementation is slightly lighter near the "0" in the colorbox.

I also see that the PNG output does not have the colorbox lined up with the axis borders as do the X11 and PostScript outputs.

Dan