How to remove glare from images in opencv?

Question

This mathematica code removes glare from an image:

img = Import["foo.png"]
Inpaint[img, Dilation[saturated, DiskMatrix[20]]]

as shown in the most upvoted answer here:

https://dsp.stackexchange.com/questions/1215/how-to-remove-a-glare-clipped-brightness-from-an-image

I want to use opencv instead of Mathematica to get the same result. How would I write equivalent code in opencv-python?

Answer 1

Here is how to do that in Python/OpenCV.

But I do not think the OpenCV inpainting routines are working or at least are not working well for my Python 3.7.5 and OpenCV 3.4.8.

Input:

import cv2
import numpy as np

# read image
img = cv2.imread('apple.png')

# convert to gray
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

# threshold grayscale image to extract glare
mask = cv2.threshold(gray, 220, 255, cv2.THRESH_BINARY)[1]

# Optionally add some morphology close and open, if desired
#kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (7,7))
#mask = cv2.morphologyEx(mask, cv2.MORPH_CLOSE, kernel, iterations=1)
#kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (3,3))
#mask = cv2.morphologyEx(mask, cv2.MORPH_OPEN, kernel, iterations=1)


# use mask with input to do inpainting
result = cv2.inpaint(img, mask, 21, cv2.INPAINT_TELEA) 

# write result to disk
cv2.imwrite("apple_mask.png", mask)
cv2.imwrite("apple_inpaint.png", result)

# display it
cv2.imshow("IMAGE", img)
cv2.imshow("GRAY", gray)
cv2.imshow("MASK", mask)
cv2.imshow("RESULT", result)
cv2.waitKey(0)

Thresholded image:

Result: