title: Specify background color when rotating an image using OpenCV in Python
body: <p>I'm trying to rotate an image in Python using OpenCV with the following code:</p>
  
  <pre><code>import cv2
  
  img = cv2.imread("image.png")
  
  rows = img.shape[0]
  cols = img.shape[1]
  
  img_center = (cols / 2, rows / 2)
  M = cv2.getRotationMatrix2D(img_center, 45, 1)
  
  rotated_image = cv2.warpAffine(img, M, (cols, rows))
  </code></pre>
  
  <p>The code works as it should, but the background where the image is no longer visible turns black. I want the background to be white and I'm therefore wondering if it's possible to specify the color <code>OpenCV</code> should use for it when rotating.</p>
  
  <p>I found a <a href="https://stackoverflow.com/questions/49510225/rotating-image-in-python-extrapolate-background-color">similar question</a> but for <code>PIL</code>.</p>