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Composition attribute in HTML5 Canvas?

HTML5 canvas provides compositing attribute globalCompositeOperation that affect all the drawing operations.

<!DOCTYPE HTML>
<html>
   <head>
      <script>
         var compositeTypes = [
            'source-over','source-in','source-out','source-atop',
            'destination-over','destination-in','destination-out',
            'destination-atop','lighter','darker','copy','xor'
         ];

         function drawShape(){
            for (i = 0; i < compositeTypes.length; i++){
               var label = document.createTextNode(compositeTypes[i]);
               document.getElementById('lab'+i).appendChild(label);
               var ctx = document.getElementById('tut'+i).getContext('2d');

               // draw rectangle
               ctx.fillStyle = "#FF3366";
               ctx.fillRect(15,15,70,70);

               // set composite property
               ctx.globalCompositeOperation = compositeTypes[i];

               // draw circle
               ctx.fillStyle = "#0066FF";
               ctx.beginPath();
               ctx.arc(75,75,35,0,Math.PI*2,true);
               ctx.fill();
            }
         }
      </script>
   </head>
   <body onload = "drawShape();">
      <table border="1" align = "center">
         <tr>
            <td><canvas id = "tut0" width = "125" height = "125"></canvas><br/>
            <label id = "lab0"></label>
            </td>
            <td><canvas id = "tut1" width = "125" height = "125"></canvas><br/>
            <label id = "lab1"></label>
            </td>
            <td><canvas id = "tut2" width = "125" height = "125"></canvas><br/>
            <label id = "lab2"></label>
            </td>
         </tr>

         <tr>
            <td><canvas id = "tut3" width = "125" height = "125"></canvas><br/>
            <label id = "lab3"></label>
            </td>
            <td><canvas id = "tut4" width = "125" height = "125"></canvas><br/>
            <label id = "lab4"></label>
            </td>
            <td><canvas id = "tut5" width = "125" height = "125"></canvas><br/>
            <label id = "lab5"></label>
            </td>
         </tr>

         <tr>
            <td><canvas id = "tut6" width = "125" height = "125"></canvas><br/>
            <label id = "lab6"></label>
            </td>
            <td><canvas id = "tut7" width = "125" height = "125"></canvas><br/>
            <label id = "lab7"></label>
            </td>
            <td><canvas id = "tut8" width="125" height = "125"></canvas><br/>
            <label id = "lab8"></label>
            </td>
         </tr>

         <tr>
            <td><canvas id = "tut9" width = "125" height = "125"></canvas><br/>
            <label id = "lab9"></label>
            </td>
            <td><canvas id = "tut10" width = "125" height = "125"></canvas><br/>
            <label id = "lab10"></label>
            </td>
            <td><canvas id = "tut11" width = "125" height = "125"></canvas><br/>
            <label id = "lab11"></label>
            </td>
         </tr>
      </table>
   </body>
</html>
Updated on 29-Jan-2020 10:16:39

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