title: Get intermediate color from a gradient
body: <p>Say I have a liner gradient as shown:</p>
  
  <pre><code>QLinearGradient linearGrad(QPointF(0, 0), QPointF(0, 100));
  linearGrad.setColorAt(1, Qt::red);
  linearGrad.setColorAt(0.5, Qt::yellow);
  linearGrad.setColorAt(0, Qt::green);
  </code></pre>
  
  <p>How to get the color of the point QPointF(0, 28.5) in this gradient?</p>
  
  <p>Indeed I want to have this kind of color distribution to be able to choose intermediate colors. I don't care if it is done by using QLinearGradient or something else.</p>