How to change Matplotlib color bar size in Python?

Last Updated : 03 Jan, 2021

Colorbar is a separate axis that provides a current colormap indicating mapping of data-points into colors. In this article, We are going to change Matplotlib color bar size in Python. There are several ways with which you can resize your color-bar or adjust its position. Let’s see it one by one.

Method 1: Resizing color-bar using shrink keyword argument

Using the shrink attribute of colorbar() function we can scale the size of the colorbar.

Syntax : matplotlib.pyplot.colorbar(mappable=None, shrink=scale)

Basically, we are multiplying by some factor to the original size of the color-bar. In the below example by using 0.5 as a factor, We are having the original color-bar size.

Example 1:

Python3

# importing library 
import matplotlib.pyplot as plt 
  
# Some data to show as an image 
data = [[1, 2, 3], 
        [4, 5, 6]] 
  
# Call imshow() to display 2-D data as an image 
img = plt.imshow(data) 
  
# Scaling colorbar by factor 0.5 
plt.colorbar(shrink=0.5) 
plt.show() 

Output:

Using_shrink_attribute

Example 2: In this example, we are using factor 0.75. Similarly, you can use any factor to change the color-bar size. The default value of the shrink attribute is 1.

Python3

import matplotlib.pyplot as plt 
import matplotlib.image as mpimg 
fig, ax = plt.subplots() 
  
# getting rid of axis 
plt.axis('off') 
  
# Reading saved image from folder 
img = mpimg.imread(r'img.jpg') 
  
# displaying image 
plt.imshow(img) 
  
# Scaling by factor 0.75 
plt.colorbar(shrink=0.75) 
plt.show() 

Output:

Using_shrink_attribute

Method 2: Using AxesDivider class

With this class, you can change the size of the colorbar axes however height will be the same as the current axes. Here we are using axes_divider.make_axes_locatable function which returns the AxisDivider object for our current axes in which our image is shown.

Example:

Python3

# importing libraries 
import matplotlib.pyplot as plt 
from mpl_toolkits.axes_grid1 import make_axes_locatable 
  
fig, ax = plt.subplots() 
# Reading image from folder 
  
img = mpimg.imread(r'img.jpg') 
image = plt.imshow(img) 
  
# Locating current axes 
divider = make_axes_locatable(ax) 
  
# creating new axes on the right 
# side of current axes(ax). 
# The width of cax will be 5% of ax 
# and the padding between cax and ax 
# will be fixed at 0.05 inch. 
colorbar_axes = divider.append_axes("right", 
                                    size="10%", 
                                    pad=0.1) 
# Using new axes for colorbar 
plt.colorbar(image, cax=colorbar_axes) 
plt.show() 