[Matplotlib-users] Different colors between imshow and patches

[Jens Nielsen]

It looks like a bug in the OSX backend. I can reproduce with the OSX
backend but it looks correct with any other backend that also explains why
the saved images looks correct.
If you have other GUI toolkits installed you can switch by adding

import matplotlib
matplotlib.use('Qt4Agg') #Or any other backend

before importing pyplot the first time

best
Jens

On Wed, 13 Jan 2016 at 11:08 David Bourgeois <david at jaguarondi.com> wrote:

> In Matplotlib, images and patches are shown on screen with different color
> rendering, at least with my setup. The following script displays an image
> of a grayscale (np.array) overlaid at the center with the same grayscale
> generated from matplotlib.patches.
>
> There is a difference of gamma between the image and the patches on what's
> displayed on screen but if I save this figure, then the resulting file is
> correct. Checking with some graphic software, the patches are displaying
> the correct color, not the image.
>
> Snapshot:
> http://i.stack.imgur.com/mv8aU.jpg
>
> Saving the figure from the figure window 'save' button gives this:
> http://i.stack.imgur.com/fVNnh.png
>
> Is there anything I'm missing in this code?
>
>     import numpy as np
>     import matplotlib.pyplot as plt
>     from matplotlib.patches import Rectangle
>
>     color = np.zeros(3)
>
>     f, ax = plt.subplots()
>     im = np.zeros((1000, 1100,3))
>     for i in range(11):
>         im[:,i*100:(i+1)*100,:] = np.tile(np.array([[color]]), (1000, 100,
> 1))
>         ax.add_patch(Rectangle((i*100,300), 100, 400, linewidth=0,
> facecolor=color))
>         color = color + 0.1
>     plt.imshow(im)
>     plt.show()
>
> I'm on OSX, so I also checked the color management and by changing the
> color profile of my display, both image and patches are affected so I guess
> color management is not where the problem lies.
>
> Thank you,
> David
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