Re: A key sample for pm3d surfaces?

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

On 07/07/2016 01:53 PM, Ethan A Merritt wrote:
> On Thursday, 07 July, 2016 12:19:21 Daniel J Sebald wrote:
>> I'm trying to add a key sample for a pm3d surface.  I know there is the
>> color box and all, but it seems odd that there can be a title entry in
>> the key but no sample.  I can sort of kludge a solution by leaving the
>> surface title empty and then create a bogus line with NaN's that will
>> contain the sample and title, linewidth 8.  For the Qt terminal, the
>> default is rounded line ends so the key sample at linewidth 8 is round.
>>
>> Basically, it would be nice to have a sample entry for surface similar
>> in appearance to the filledcurve or candlestick of 2D plots.  I wonder
>> if it would make sense to have a "sample" descriptor in plot/splot lines
>> similar to the "title" descriptor.
>
> The problem with using a colored key sample for anything with pm3d
> coloring (surfaces or anything else) is that it is not clear how to
> choose a color for the sample.   You might for example have 3 plots
> in a single figure using the same pm3d palette, one plot predominantly
> green, one predominantly blue, and one predominantly yellow.
> You would like the key to match, but how would the program know this?

That's a good example of the use.  As a default, key sample is sort of 
meaningless for surfaces--I suppose something like average color might 
show predominant color and somehow make surfaces distinct.  The default 
could be blank, but I was thinking something that the user could 
specify, e.g.,

   plot 'foo.dat' with pm3d title 'green component' sample rgb 'green'

where sample for pm3d would be have FILLSTYLE bit set so that it comes 
out as a patch rather than a line.  I've kind of achieved this with an 
extra bogus line of width 11 to contain the title.  It's roughly the 
same size as a key sample patch.

Dan