[Plplot-general] rgb colourscale interpolation

[Phil R. <p.d...@gm...>]

Hi All
Somehow I feel like we may have had this discussion before, but I'm not sure.

If I call plscmap1l or plscmap1la using rgb colours, then these
colours are converted to hls colours and interpolated in hls space,
this is counter to what I might expect and not documented.

So for example I just tried to do a plot with a colourscale going from
red to blue specifying rgb colours. So I expected it to give me a
colourscale going from red, through shades of purple to blue. But
instead I got a rainbow colour scheme as the interpolation in hls
space goes round the colour wheel.

I feel that if someone provides colours in rgb values we really should
interpolate in rgb values. Or at the very least we need to make it
very clear in the documentation that we always interpolate in hls
space even if colours are provided as rgb.

Any thoughts?

Phil