CODEWITHSUNDEEP
javascripthtmlcanvashtml5-canvasdrawimage
Muhammad Usman
Muhammad Usman

Reputation: 10946

drawImage (canvas) is not working

I want to draw multiple canvases on a single canvas using drawImage() method but it is not working Code

<html>
 <head>
  <script>
    window.onload = function() {
    var context1= document.getElementById("canvas1").getContext("2d");
    var context2  = document.getElementById("canvas2").getContext("2d");
    var context3  = document.getElementById("canvas3").getContext("2d");

    context1.font = "20pt Calibri";
    context1.fillStyle = "blue";
    context1.fillText("Hello ", 50, 25);

    context2.font = "20pt Calibri";
    context2.fillStyle = "red";
    context2.fillText("World!", 100, 25);

    var imageObj = new Image();
     imageObj.onload = function() {
      context3.drawImage(context1.canvas, 50, 25);
      context3.drawImage(context2.canvas, 100, 25);
        };
  };

</script>
 </head>
<body>
<canvas id="canvas1" class="canvas" width="200" height="50"></canvas>
<canvas id="canvas2" class="canvas" width="200" height="50"></canvas>
<canvas id="canvas3" class="canvas" width="200" height="50"></canvas>
</body>
</html>​

JS Fiddle http://jsfiddle.net/4xT2j/2/

Upvotes: 1

Views: 13678

Answers (2)

Denys S&#233;guret
Denys S&#233;guret

Reputation: 382464

Your images have no source. Add one if you want to see something. The onload function cannot be called as long as you don't have a src.

And you must provide the image to the drawImage function :

 var imageObj = new Image();
 imageObj.onload = function() {
   context3.drawImage(imageObj, 50, 25);
   context3.drawImage(imageObj, 100, 25);
 };
 imageObj.src = "someFile.png";

If what you're trying to do is draw canvas1 and canva2 on context3, simply do all this outside the imageObj.onload function which is never called : http://jsfiddle.net/KCyvE/

A precision following a question in comment :

My code in the fiddle uses context1.canvas. This works because The context is an instance of CanvasRenderingContext2D and thus has a property named canvas which is a "Back-reference to the canvas element for which this context was created".

Upvotes: 6

bennedich
bennedich

Reputation: 12367

Your imageObj.onload function is somewhat wrong. This is what you want: http://jsfiddle.net/4xT2j/3/

Please observe there isn't necessarily a reason to write canvas3 to an image object since it already is an image object.

Upvotes: 1

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