HTML5 canvas: image resizing

Question

I'm trying to place an image on a canvas without resizing it. I thought drawImage(img, x, y) would do the trick, but it stretches the image to fill the canvas. Also supplying drawImage(img, x, y, width, height) with the dimensions of my image doesn't seem to work.

Here's my code:

<canvas id="story" style="position:relative; width:800px; height:600px;"></canvas>

<script type="text/javascript">

window.onload = function() {
  var canvas = document.getElementById("story");
  var context = canvas.getContext("2d");
  var img = document.getElementById("img1");
  var width = parseInt(img.width);
  var height = parseInt(img.height);
  context.drawImage(img, 0, 0, width, height);
}

</script>
<img id="img1" alt="" src="http://link to image"/>

Thanks in advance!

PS: I added the parseInt's to make sure that drawImage gets valid values.

Answer 1

Don't use CSS to size your canvas. That creates a default sized canvas and stretches it. Set the canvas dimensions directly on it and you'll get a 1 to 1 pixel drawing space.

<canvas id="story" width="800" height="600" style="position:relative;"></canvas>

Answer 2

Trochoid is right, the style attribute on your canvas tag is causing problems. You could set it in the HTML, as he suggests, or better yet you can leave it blank and set it dynamically in the JS:

<canvas id="story"></canvas>

<script type="text/javascript">

window.onload = function() {
      var canvas = document.getElementById("story");
      var context = canvas.getContext("2d");
      var img = document.getElementById("img1");
      var width = parseInt(img.width);
      var height = parseInt(img.height);

      canvas.height=height;
      canvas.width=width;
      context.drawImage(img, 0, 0);
}

</script>
<img id="img1" alt="" src="http://link to image"/>