title: HowTo create legend for google Heatmap?
body: <p>I have drawn heatmap using Google maps API v3 with the DB application at the backend.</p>
  
  <p>Cool, I see green.->.yellow.->.red fradient over my map. Looks fine!</p>
  
  <p>But how can I get values for these colors?</p>
  
  <p>What's avg weight for light-green color and dark-red?</p>
  
  <p>Can I implement such "legend" using goolge API or I need to write some kind of custom JS functionality?</p>