Re: [Matplotlib-users] Colormap norm (vmin, vmax) based on visible part of figure

[Benjamin R. <ben...@ou...>]

On Sun, Dec 16, 2012 at 4:41 PM, David Huard <dav...@gm...> wrote:

> Hi all,
>
> I'm wondering if anyone knows how to compute colorbar limits (vmin, vmax)
> based only on the visible portion of the figure. My use-case is a
> pcolormesh(x, y, z) drawn over a Basemap instance. The coordinates x and y
> cover the entire globe, but I'm only mapping the Arctic. What happens is
> that the normalization is done over the entire z array, while only a subset
> of z actually appears on the map.  The colors appearing on the map thus
> cover only a small fraction of the entire color range.
>
> From what I managed to understand, pcolormesh creates a collections of
> patches colorcoded based on the array attribute. So my question is if there
> is a builtin way to know which items of this collections are clipped so I
> can mask this part of the array ?
>
> Thanks a lot,
>
> David
>
>
As far as I know, no, there is not a built-in way of doing so.  There is
the clipping mechanism to prevent drawing things outside of bounding boxes
(used for easy zooming and panning among other things), but as far as I
know, that is done mostly in the backends, and it doesn't provide
information on which elements in the array was chosen drawn.  I would
suggest making a feature request on the github page, and hopefully, someone
will have an epiphany on how to implement such a feature (maybe with the
scalar mappable objects?).

Cheers!
Ben Root