Re: [matplotlib-devel] [PATCH] Discontinuous colormaps are reversed incorrectly

[Eric F. <ef...@ha...>]

On 10/01/2010 03:59 PM, Stan West wrote:
> Hi, developers. I stumbled upon this when I noticed that gist_stern_r
> isn't the reverse of gist_stern. As the attached script shows, the
> discontinuity in red is wrong, and green stays zero instead of ramping.
> The problem seems to be that when cm.revcmap() reverses a linear segment
> map spec (such as {'red': [(0, 0, 0), (0.5, 1, 1), (1, 1, 1)], ...}), it
> doesn't swap the second and third elements of each tuple—the color
> values facing in each direction. That makes no difference for continuous
> colormaps but distorts discontinuous maps such as gist_stern. I believe
> that the attached "cm.patch" file fixes the problem.
>
> The other patch, "_cm.patch", is only aesthetic after the above patch is
> applied. It changes an element of the gist_stern colormap spec that
> should have been unused but which caused the green channel to stay at
> zero with the old revcmap. With the patched revcmap, the changed element
> should not be used, but the colormap spec will look like most others
> with the second and third elements of the tuple being equal.
>

Patches committed in 8725.  Thank you.

Eric