Canvas: Difference between revisions

Revision as of 17:07, 25 September 2012

The canvas tag was introduced by Apple and has been standardized to become part of HTML5.

To use it, you add the canvas tag to your HTML page, then use javascript draw on it.

<canvas id="canvas" showsrc> function draw() {

 c = document.getElementById("canvas");
 p = c.getContext("2d");
 p.fillRect(50, 50, 150, 150);

} </canvas>

See Looping with canvas

Template

A complete HTML page with canvas tag + javascript to draw in it, note how the draw function is first defined (in the script tag) and then finally called by the body "onload". This ensures that the page is fully loaded before the drawing is performed.

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<script>
// Define a draw function that contains your
// drawing code
function draw(){
  c = document.getElementById("canvas")
  //console.log("c is",c)
  p = c.getContext("2d")
  p.fillRect(50, 50, 150, 150);
}
</script>
</head>
<!-- The body tag then will call draw() when the page has loaded -->
<body onload="draw()">
<canvas id="canvas" width="250" height="250" style="border: 1px solid black"></canvas>
</body>
</html>

Links

@@ Line 42: / Line 42: @@
 * [http://developer.mozilla.org/en-US/docs/Canvas_tutorial Mozilla canvas Tutorial]
-* [http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html The official specification]
+* [http://www.whatwg.org/specs/web-apps/current-work/multipage/the-canvas-element.html The official canvas specification]
 * [http://www.effectgames.com/demos/canvascycle/ An example for color cycling with the canvas element]