title: Get canvas size from its context
body: <p>I'm building a few libraries for canvas graphing in javascript, and I was wondering if there was any way to get the size of the canvas from it's 2D context. I was looking for something like this.</p>
  
  <pre><code>var size=ctx.size;
  scale=size/100;
  </code></pre>
  
  <p>There are multiple canvas elements here, so I can't do canvas.width.
  <br>Thanks</p>