title: How to give browser "save image as" option to button
body: <p>I'm working on a canvas drawing project. I convert the canvas as an image, then I save that image as '.png'. I have to right click on the image and select the 'save image as' option. But I want to provide that option through a button. When I click the button it should be saved. </p>
  
  <p>Any example or idea would be appreciated.</p>
  
  <p>This is a js function that converts canvas to png.</p>
  
  <pre><code> function save2()
   {
     window.open(canvas.toDataURL('image/png'));
     var gh=(canvas.toDataURL('png'));
     alert("converted");
   }
  </code></pre>