How to map number to color using matplotlib's colormap?

Question

Consider a variable x containing a floating point number. I want to use matplotlib\'s colormaps to map this number to a color, but not plot anything. Basically,

Answer 1

You can get a color from a colormap by supplying an argument between 0 and 1, e.g. cm.autumn(0.5).

If there is a normalization instance in the game, use the return of the Normalization instead:

import matplotlib.cm as cm
from matplotlib.colors import Normalize

cmap = cm.autumn
norm = Normalize(vmin=-20, vmax=10)
print cmap(norm(5))

Answer 2

It's as simple as cm.hot(0.3), which returns (0.82400814813704837, 0.0, 0.0, 1.0).

A full working program could read

import matplotlib.cm as cm

print(cm.hot(0.3))

If you also want to have the normalizer, use

import matplotlib as mpl
import matplotlib.cm as cm

norm = mpl.colors.Normalize(vmin=-20, vmax=10)
cmap = cm.hot
x = 0.3

m = cm.ScalarMappable(norm=norm, cmap=cmap)
print(m.to_rgba(x))

Answer 3

Number value to colormap color

import matplotlib.cm as cm
import matplotlib as matplotlib

def color_map_color(value, cmap_name='Wistia', vmin=0, vmax=1):
    # norm = plt.Normalize(vmin, vmax)
    norm = matplotlib.colors.Normalize(vmin=vmin, vmax=vmax)
    cmap = cm.get_cmap(cmap_name)  # PiYG
    rgb = cmap(norm(abs(value)))[:3]  # will return rgba, we take only first 3 so we get rgb
    color = matplotlib.colors.rgb2hex(rgb)
    return color