Question

I’m trying to display an image using OpenCV. I have the following very basic code:

import cv2

img = cv2.imread('myimage.png', 0)  # Reads a Gray-scale image
img2 = cv2.cvtColor(img, cv2.COLOR_GRAY2BGR)
cv2.imshow("window", img2)

The window is opened properly, with the correct size, but it’s gray – there’s no image. The image is read properly (looking at both img and img2 in the debugger I see the expected values, not just one shade).

Note: Obviously I intend to do some image processing prior to showing the image, but first I need to be able to see the image…

Answer 1

OK, got it.

Turns out I needed to let OpenCV start handling events, it wasn’t handling the WM_PAINT event. Adding cv2.waitKey() fixed this.