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I am trying to convert a color image (RGB, 24 bit, png) to grayscale using OpenCV. But I am getting unexpected results. I have tried the following 3 approaches, which all give the same result.
Method 1:

img=cv2.imread(file)
img=cv2.cvtColor(img, cv2.COLOR_RGB2BGR)
plt.imshow(img)
temp=cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
plt.imshow(temp)

Method 2:

img=cv2.imread(file)
plt.imshow(img)
temp=cv2.cvtColor(img, cv2.COLOR_RGB2GRAY)
plt.imshow(temp)

Method 3:

img=cv2.imread(file,0)
img=cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
plt.imshow(img)

The original image is:
enter image description here
The image I am getting after the above conversions is:
enter image description here

I assume the problem lies in the channels (BGR being default for OpenCV imread). I need a proper grayscale image. Any help is appreciated. Thank You!

Improve this question
3
  • 1
    Have a read here... stackoverflow.com/a/61505879/2836621 Commented May 3, 2020 at 13:57
  • 2
    Also, you need to use cmap='gray' else you get the Viridis colormap. Commented May 3, 2020 at 13:59
  • Thank you so much! The problem as mentioned in the link was that I was using another library. Commented May 3, 2020 at 14:13
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