javascript - How can I put multiple canvas elements in to one canvas element? -


i have multiple canvas elements created javascript. question is: "how can put multiple canvas elements 1 canvas element?".

here go;

jsfiddle

  • it grab each canvas , make them png's
  • access buffer canvas , write png's on top of each other inside it
  • write buffer canvas png , send img-tag

just give #buffer canvas element display: none; , happen invisible (check here; http://jsfiddle.net/allendar/uqxcy/2/).

html

<body onload="generatepng()">     <canvas id="c1"></canvas>     <canvas id="c2"></canvas>     <canvas id="c3"></canvas>      <canvas id="buffer"></canvas>      <div id="output">empty</div> </body>

css

canvas[id^=c], div[id=output] {     border: 1px solid red; }  canvas[id=buffer] {     border: 1px dotted green; }  #output {     padding: 15px; }  #output img {     border: 1px dotted blue; }

javascript

function generatepng() {     var b_canvas1 = document.getelementbyid("c1");     var b_context1 = b_canvas1.getcontext("2d");     b_context1.fillrect(10, 50, 50, 50);     var b_canvas2 = document.getelementbyid("c2");     var b_context2 = b_canvas2.getcontext("2d");     b_context2.fillrect(80, 50, 50, 50);     var b_canvas3 = document.getelementbyid("c3");     var b_context3 = b_canvas3.getcontext("2d");     b_context3.fillrect(150, 50, 50, 50);      var img1 = new image();     img1.src = b_canvas1.todataurl("image/png");     var img2 = new image();     img2.src = b_canvas2.todataurl("image/png");     var img3 = new image();     img3.src = b_canvas3.todataurl("image/png");      var buffer = document.getelementbyid("buffer");     var buffer_context = buffer.getcontext("2d");     buffer_context.drawimage(img1, 0, 0);     buffer_context.drawimage(img2, 0, 0);     buffer_context.drawimage(img3, 0, 0);      var buffer_img = new image();     buffer_img.src = buffer.todataurl("image/png");      var output = document.getelementbyid('output');     output.innerhtml = '<img src="' + buffer_img.src + '" alt="canvas image" />'; }

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