CODEWITHSUNDEEP
pythoncomputer-visionopencvgrayscaleimage-thresholding
Conor Casey
Conor Casey

Reputation: 39

Threshold an image using RBG

I would like to threshold an image, but instead of the output being black and white I would like it to be white and some other color. I was able to achieve this using a nested for-loop however this is slow and I was wondering if anyone knows any method of doing this efficiently using CV2 functionality.

img = cv2.imread("Naas.png", 1)
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
threshold, thresh = cv2.threshold(gray, 150, 255, cv2.THRESH_BINARY)

# Changing black to green and converting from Grayscale to RGB

lis = []
for i in thresh:
    for j in i:
        if j == 0:
            lis.append((0, 255, 0))
        else:
            lis.append((255, 255, 255))
        
img = np.array(lis, dtype = "uint8")
img = img.reshape(thresh.shape[0], thresh_inv.shape[], 3)

This loop changes any black pixels to green in the thresholded image.

Upvotes: 1

Views: 1060

Answers (1)

Thijser
Thijser

Reputation: 2633

So the green channel is always 255 and the red and blue channels are just the threshold values?

So you are looking at something like this

import numpy as np 
img = cv2.imread("Naas.png", 1)
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
threshold, thresh = cv2.threshold(gray, 150, 255, cv2.THRESH_BINARY)
img_result=np.ones(img.shape)*255 #set all to 255
img_result[:,:,0]=thresh[:,:] #set red channel to threshold
img_result[:,:,2]=thresh[:,:] #set blue channel to threshold

Upvotes: 1

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