canvas-7globleCompositeOperation.html

12/6/2015来源:Javascript教程人气:463

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <canvas id="canvas" style="margin:0 auto;border:1px #ddd solid">
        The current browser does not support Canvas, can replace the browser a try!
    </canvas>

    <script>

        window.onload = function(){
            var canvas = document.getElementById('canvas');

            canvas.width = 1024;
            canvas.height = 768;

            if(canvas.getContext('2d')){
                var context = canvas.getContext('2d');

                context.fillStyle = "blue";
                context.fillRect(100,200,400,400);

                context.globalCompositeOperation = "sourse-over";
                context.fillStyle = "red";
                context.beginPath();
                    context.moveTo(400,300);
                    context.lineTo(650,700);
                    context.lineTo(150,700);
                context.closePath();
                context.fill();

            }else{
                alert('当前游览器不支持Canvas,请更换游览器后再试!');
            }
        }

    </script>
</body>
<script>
    /*global

        globalAlpha

        globalCompositeOperation  = "source-over"(default)
                                    sourse-atop
                                    sourse-in
                                    sourse-out

                                    destination-over  //前面绘制的覆盖了后面绘制的图形
                                    destination-atop
                                    destination-in
                                    destination-out

                                    lighter
                                    copy
                                    xor
                
    */
</script>
</html>