title: Change color of a pixel with OpenCV
body: <p>Let say I have this rose (Do not care about the background, only the white leaves are important).</p>
  
  <p><img src="https://i.stack.imgur.com/5585T.jpg" alt="enter image description here"></p>
  
  <p>I transform it to a grayscale picture: 
  <code>grayscaled=cv2.imread('white_rose.png',cv2.IMREAD_GRAYSCALE)</code></p>
  
  <p>How can I change every white pixel to a red one under the condition the red color (<code>R=255</code>) will have the same contrast as the white one has ? Meaning I want to see the white leaves in red color but with the same <code>L</code> value of every pixel that in <code>grayscaled</code> ?</p>