How to Draw Rectangle on Image in Matplotlib?

Prerequisites: Matplotlib

Given an image the task here is to draft a python program using matplotlib to draw a rectangle on it. Matplotlib comes handy with rectangle() function which can be used for our requirement.

Syntax: Rectangle(xy, width, height, angle=0.0, **kwargs)

Parameters:

• xy: Lower left point to start the rectangle plotting
• width : width of the rectangle
• height: Height of the rectangle.
• angle: Angle of rotation of the rectangle.

Approach

• Import the necessary libraries. 
• Insert and display the image.
• Create the figure and axes of the plot 
• Add the patch to the Axes
• Display the image

Example 1: Draw a rectangle on an image

Python3

import matplotlib.pyplot as plt
import matplotlib.patches as patches
from PIL import Image
import numpy as np

x = np.array(Image.open('geek.png'), dtype=np.uint8)
plt.imshow(x)

# Create figure and axes
fig, ax = plt.subplots(1)

# Display the image
ax.imshow(x)

# Create a Rectangle patch
rect = patches.Rectangle((50, 100), 40, 30, linewidth=1,
                         edgecolor='r', facecolor="none")

# Add the patch to the Axes
ax.add_patch(rect)
plt.show()

Output:

original image

image with rectangle

Example 2: Draw a filled rectangle

Python3

import matplotlib.pyplot as plt
import matplotlib.patches as patches
from PIL import Image
import numpy as np

x = np.array(Image.open('geek.png'), dtype=np.uint8)
plt.imshow(x)

# Create figure and axes
fig, ax = plt.subplots(1)

# Display the image
ax.imshow(x)

# Create a Rectangle patch
rect = patches.Rectangle((50, 100), 40, 30, linewidth=1,
                         edgecolor='r', facecolor="g")

# Add the patch to the Axes
ax.add_patch(rect)
plt.show()

Output:

original image

image with rectangle