Is there any good color map to convert gray-scale image to colorful ones using python's PIL? [duplicate]

Question

Matplotlib has a lot of good color maps, but is bad in performance. I'm writing some code to make gray-scale image colorful where interpolate with color map is a good idea. I wonder whether there are open source color maps available or demo code to use Pillow to convert gray-scale images into colorful ones via colormap?

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Clarify:

1. Matplotlib is good for demo use, but bad performace for thounsands of images.
2. Matplotlib colormaps
3. You can map grayscale images to colormaps to get colorful ones.

Demo:

The first image is grayscale, second is mapped in 'jet' cmap, third being 'hot'.

The problem is that I do not know much about colors, and I'd like to achieve such effects in PIL for better performance.

Answer 1

You can use the color maps from matplotlib and apply them without any matplotlib figures etc. This will make things much faster:

import matplotlib.pyplot as plt

# Get the color map by name:
cm = plt.get_cmap('gist_rainbow')

# Apply the colormap like a function to any array:
colored_image = cm(image)

# Obtain a 4-channel image (R,G,B,A) in float [0, 1]
# But we want to convert to RGB in uint8 and save it:
Image.fromarray((colored_image[:, :, :3] * 255).astype(np.uint8)).save('test.png')

Note:

• If your input image is float, the values should be in the interval [0.0, 1.0].

• If your input image is integer, the integers should be in the range [0, N) where N is the number of colors in the map. But you can resample the map to any number of values according to you needs:

  # If you need 8 color steps for an integer image with values from 0 to 7:
  cm = plt.get_cmap('gist_rainbow', lut=8)