Region of interest with Python

Often when doing computer vision tasks, it's not the entire image or photograph you are interested in.

A photo of scene may be contain many different objects that need to be classified each. so how do you achieve that?

You can use region-of-interest. A region of the image that is important.

Lets say you want to recognize faces, given a photo a person, you don't need the hat or the clothes, you need a close up of the face.

In Python you can easily do that. If you load an image like this

#!/usr/bin/python3
import cv2
import numpy as np


img = cv2.imread("lena.png", cv2.IMREAD_UNCHANGED)
cv2.imshow("Demo", img)

Then you can create a region of interest like this

face = np.ones((200, 150, 3))
face = img[200:400, 200:350]
cv2.imshow("face", face)
cv2.waitKey(0)
cv2.destroyAllWindows()

So the complte code

#!/usr/bin/python3
import cv2
import numpy as np

img = cv2.imread("lena.png", cv2.IMREAD_UNCHANGED)
face = np.ones((200, 150, 3))
cv2.imshow("Demo", img)
face = img[200:400, 200:350]
cv2.imshow("face", face)
cv2.waitKey(0)
cv2.destroyAllWindows()

Related links:

• How to install OpenCV for Python
• Learn Python Programming
• Python Exercises
• Computer Vision course & examples