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pythontransparencytransparentgrayscaleopencv

How can I convert an image to grey scale while keeping transparency using cv2?

At the moment my code takes an image in color and converts it to grayscale. The problem is that it makes the transparent pixels white or black.

This is what I have so far: 

import cv2

img = cv2.imread("watch.png",cv2.IMREAD_GRAYSCALE)
cv2.imwrite("gray_watch.png",img)

Here is the pic for reference: Watch.png

Solution

  • I found that using only PIL can accomplish this:

    from PIL import Image

image_file = Image.open("convert_image.png") # opens image  
image_file = image_file.convert('LA') # converts to grayscale w/ alpha
image_file.save('output_image.png') # saves image result into new file

    This preserves the transparency of the image as well. "LA" is a color mode. You can find other modes here: https://pillow.readthedocs.io/en/3.1.x/handbook/concepts.html#concept-modes