Re: [Matplotlib-users] new interface functions for LinearSegmentedColormap

Dr. Phillip M. Feldman wrote:
> After experimenting with colormaps for a while, I was able to make both
> discrete (piecewise-constant) and continuous (piecewise-linear) colormaps
> work. Although colormaps can be created directly using
> LinearSegmentedColormap from the matplotlib.colors package, this is a
> tedious and error-prone process. So, I compiled a set of three interface
> functions. (I wrote two of these myself, and got one from the SciPy
> website). The two functions that I wrote permit one to define a discrete
> (piecewise-constant) and continuous (piecewise-linear) colormap directly via
> a sequence of colors and a set of thresholds specified as lists. Each color
> may be specified either via an RGB tuple or via an English color name known
> to webcolors.name_to_rgb. I'm going to submit all of this to the matplotlib
> developers forums in the hopes of getting it incorporated into matplotlib.

Something I should have mentioned earlier: for the discrete case, one 
good option is to use a ListedColormap to make a map with only a few 
colors, and then use a BoundaryNorm to handle the mapping from data 
values to colors.  See 
http://matplotlib.sourceforge.net/examples/pylab_examples/image_masked.html?highlight=image_masked
for a BoundaryNorm example.  Unfortunately, we don't have an example of 
using it with a ListedColormap, but it should be straigtforward; the key 
point is to set the BoundaryNorm ncolors kwarg to match the actual 
number of colors in the colormap.

Eric