一般来说,matplotlib 中的颜色图是一维的,即它们将标量映射到颜色。
为了获得 2D 颜色图,需要以某种方式发明两个标量到颜色的映射。虽然这在原则上是可能的,但它不像通常的颜色图那么方便。
下面是一个示例,我们将两个参数分别映射到红色和蓝色 RGB 颜色通道,从而创建 2D 颜色图。
import matplotlib.pyplot as plt
import numpy as np
fig, ax = plt.subplots()
ax.set_aspect("equal")
x = [1,1,2,2,3,3] # xdata
y = [1,2,3,1,2,3] # ydata
p1 = [0.2,0.4,.6,.8,.6,.1] # parameter 1
p2 = [0.4,0.5,.7,.1,.3,.7] # parameter 2
# create a very simple colormap,
# mapping parameter 1 to the red channel and
# parameter 2 to the blue channel
cmap = lambda p1,p2 : (p1, 0, p2)
# put shapes at positions (x[i], y[i]) and colorize them with our
# cmap according to their respective parameters
for i in range(len(x)):
circle = plt.Circle((x[i], y[i]), 0.5, color=cmap(p1[i],p2[i]))
ax.add_artist(circle)
tx="p1: {}\np2: {}".format(p1[i],p2[i]) # create a label
ax.text(x[i], y[i], tx, ha="center", color="w", va="center")
ax.set_xlim(0,4)
ax.set_ylim(0,4)
ax.set_xlabel("x")
ax.set_ylabel("y")
# create the legend:
plt.subplots_adjust(left=0.1, right=0.65, top=0.85)
cax = fig.add_axes([0.7,0.55,0.3,0.3])
cp1 = np.linspace(0,1)
cp2 = np.linspace(0,1)
Cp1, Cp2 = np.meshgrid(cp1,cp2)
C0 = np.zeros_like(Cp1)
# make RGB image, p1 to red channel, p2 to blue channel
Legend = np.dstack((Cp1, C0, Cp2))
# parameters range between 0 and 1
cax.imshow(Legend, origin="lower", extent=[0,1,0,1])
cax.set_xlabel("p1")
cax.set_ylabel("p2")
cax.set_title("2D cmap legend", fontsize=10)
plt.show()
该方案当然可以扩展到其他(更复杂的)颜色映射以及 imshow 或 pcolormesh 图。此外,使用HSV 配色方案 https://stackoverflow.com/questions/10787103/2d-hsv-color-space-in-matplotlib与 RGB 相比可能更有利,所以matplotlib.colors.hsv_to_rgb(hsv) http://matplotlib.org/1.4.1/api/colors_api.html#matplotlib.colors.hsv_to_rgb可能会有帮助。