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pythonmatplotlibcolorbarcolormap

How to make colormaps for this image in python m?

I want to make a colormap used in the attached image colorbar. I could do it MATLAB, however, I can't seem to do it in python. So far I tried the code given below but didn't get the result I was looking for.

img = imread('/path/colorbarimage.png')
colors_from_img = img[:, 0, :]
my_cmap = LinearSegmentedColormap.from_list('my_cmap', colors_from_img, N=651)
y = random_sample((100, 100))
imshow(y, cmap=my_cmap);plt.colorbar()
Solution

  • With img[:, 0, :] you're not picking the correct column in the colorbar image (if indeed colorbarimage.png is the image you linked).

    The following works fine:

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

img = plt.imread('colorbarimage.png')

# to check the selected rectangle:
cropped_cmap = img[145:799, 70:80, :]
plt.imshow(cropped_cmap)
plt.show()


colors_from_img = img[145:799, 74, :]

my_cmap = LinearSegmentedColormap.from_list('my_cmap', colors_from_img, N=256)

y = np.random.random_sample((100, 100))
plt.imshow(y, cmap=my_cmap)
plt.colorbar()
plt.show()