canvas-7globleCompositeOperation2.html 

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<style>
    #buttons{width: 1200px;margin: 10px auto;clear:both;}
    #buttons a{font-size: 18px;display: block;float:left;margin-right: 14px;}
</style>
<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>

    <div id="buttons">
        <a href="">source-over</a>
        <a href="">source-atop</a>
        <a href="">source-in</a>
        <a href="">source-out</a>
        <a href="">destination-over</a>
        <a href="">destination-atop</a>
        <a href="">destination-in</a>
        <a href="">destination-out</a>
        <a href="">lighter</a>
        <a href="">copy</a>
        <a href="">xor</a>
    </div>

    <script>

        window.onload = function(){
            draw("source-over");

            var buttons = document.getElementById("buttons").getElementsByTagName("a");
            for(var i=0;i<buttons.length;i++){
                buttons[i].onclick = function(){
                    draw(this.text);
                    return false;
                }
            }
        }

        function draw(compositeStyle){
            var canvas = document.getElementById('canvas');

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

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

                context.clearRect(0,0,canvas.width,canvas.height);

                // draw title
                context.font = "bold 40 Arial";
                context.textAlign = "center";
                context.textBaseline = "#058";
                context.fillStyle = "#058";
                context.fillText("globalCompositeOperation =" + compositeStyle,canvas.width/2,60);

                // draw a rect
                context.fillStyle = "blue";
                context.fillRect(300,150,500,500);

                // draw a triangle
                context.globalCompositeOperation = compositeStyle;
                context.fillStyle = "red";
                context.beginPath();
                    context.moveTo(700,250);
                    context.lineTo(1000,750);
                    context.lineTo(400,750);
                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>

 

posted @ 2015-11-23 15:08  Cynthia娆墨旧染  阅读(218)  评论(0)    收藏  举报