透明的python matplotlib热图颜色条

Question

如何像这样实现python matplotlib热图颜色条？

plt.imshow(a,aspect='auto', cmap=plt.cm.gist_rainbow_r)
plt.colorbar()

Answer 1

matplotlib画廊中的此示例显示了制作自定义颜色图的一些不同方法，包括透明度：https://matplotlib.org/examples/pylab_examples/custom_cmap.html

在您的情况下，您似乎想要gist_rainbow颜色图的修改版本。您可以通过如下修改Alpha通道来实现此目的：

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.colors import LinearSegmentedColormap

# get colormap
ncolors = 256
color_array = plt.get_cmap('gist_rainbow')(range(ncolors))

# change alpha values
color_array[:,-1] = np.linspace(1.0,0.0,ncolors)

# create a colormap object
map_object = LinearSegmentedColormap.from_list(name='rainbow_alpha',colors=color_array)

# register this new colormap with matplotlib
plt.register_cmap(cmap=map_object)

# show some example data
f,ax = plt.subplots()
h = ax.imshow(np.random.rand(100,100),cmap='rainbow_alpha')
plt.colorbar(mappable=h)