title: How to set the opacity of an image drawn to a canvas with drawImageRect?
body: <p>I'm drawing to a <a href="https://docs.flutter.io/flutter/dart-ui/Canvas-class.html" rel="nofollow noreferrer">Canvas</a> in Flutter using <a href="https://docs.flutter.io/flutter/dart-ui/Canvas/drawImageRect.html" rel="nofollow noreferrer">drawImageRect</a>:</p>
  
  <pre><code>canvas.drawImageRect(image, sourceRect, destRect, _paint);
  </code></pre>
  
  <p>I have an Opacity value (a double between 0 and 1). How do I paint the image using this value (so that 0 is not visible and 0.5 is half-opacity)?</p>