Gaussian blurring with OpenCV: only blurring a subregion of an image?

Question

Is it possible to only blur a subregion of an image, instead of the whole image with OpenCV, to save some computational cost?

EDIT: One important po

Answer 1

Here's how to do it in Python. The idea is to select a ROI, blur it, then insert it back into the image

import cv2

# Read in image
image = cv2.imread('1.png')

# Create ROI coordinates
topLeft = (60, 140)
bottomRight = (340, 250)
x, y = topLeft[0], topLeft[1]
w, h = bottomRight[0] - topLeft[0], bottomRight[1] - topLeft[1]

# Grab ROI with Numpy slicing and blur
ROI = image[y:y+h, x:x+w]
blur = cv2.GaussianBlur(ROI, (51,51), 0) 

# Insert ROI back into image
image[y:y+h, x:x+w] = blur

cv2.imshow('blur', blur)
cv2.imshow('image', image)
cv2.waitKey()

Before -> After