Create a grayscale colorbar for each subplot in python

Question

I have two polygon patch plots with shading in grayscale, with each patch added to an axis. and I would like to add a colorbar underneath each subplot.
I’m using

import matplotlib.patches as mpatches
import matplotlib.pyplot as plt 

poly=mpatches.Polygon(verts,color=rgb,ec='black') #create patch 
ax.add_patch(poly) #add patch to axis 

plt.set_cmap('gray') #grayscale colormap 

        #verts,rgb input created in above lines of code

The colorbars should be in grayscale and have range [0,1], with 0 being black, 0.5 marked, and 1 being white. im using subplot(121) and (122).
Thanks in advance.

Asked By: mdj15

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Source

Answer 1

To use colorbars you have to have some sort of ScalarMappable instance (this is used for imshow, scatter, etc.):

mappable = plt.cm.ScalarMappable(cmap='gray')
# the mappable usually contains an array of data, here we can
# use that to set the limits
mappable.set_array([0,1])   
ax.colorbar(mappable)

Answered By: hitzg

Answer 2

I might be late here but now matplotlib has unique functionality to set colormap to gray as shown in this link.

plt.gray()
fig = plt.figure(figsize=(10, 10))
plt.subplots_adjust(left = 0, right = 1, top = 1, bottom = 0)
im = plt.imshow(output)
pos = fig.add_axes([0.93, 0.1, 0.02, 0.35])  # Set colorbar position in fig
fig.colorbar(im, cax=pos)  # Create the colorbar
plt.savefig(os.path.join(args.output_path, image_name))

the line 1 will set your colormap to grayscale. the result is shown in the image.

Answered By: Ali Waqas

Create a grayscale colorbar for each subplot in python

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