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html5实现canvas阴影效果示例

2014-05-07 16:23 696 查看
在HTML5中实现Canvas阴影效果

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="X-UA-Compatible" content="chrome=IE8">
<meta http-equiv="Content-type" content="text/html;charset=UTF-8">
<title>Canvas Clip Demo</title>
<link href="default.css" rel="stylesheet" />
    <script>
        var ctx = null; // global variable 2d context
        var imageTexture = null;
        window.onload = function() {
            var canvas = document.getElementById("text_canvas");
            console.log(canvas.parentNode.clientWidth);
            canvas.width = canvas.parentNode.clientWidth;
            canvas.height = canvas.parentNode.clientHeight;
             
            if (!canvas.getContext) {
                console.log("Canvas not supported. Please install a HTML5 compatible browser.");
                return;
            }
            var context = canvas.getContext('2d');
             
            // section one - shadow and blur
            context.fillStyle="black";
            context.fillRect(0, 0, canvas.width, canvas.height/4);
            context.font = '60pt Calibri';
             
            context.shadowColor = "white";
            context.shadowOffsetX = 0;
            context.shadowOffsetY = 0;
            context.shadowBlur = 20;
            context.fillText("Blur Canvas", 40, 80);
            context.strokeStyle = "RGBA(0, 255, 0, 1)";
            context.lineWidth = 2;
            context.strokeText("Blur Canvas", 40, 80);
             
            // section two - shadow font
            var hh = canvas.height/4;
            context.fillStyle="white";
            context.fillRect(0, hh, canvas.width, canvas.height/4);
            context.font = '60pt Calibri';
             
            context.shadowColor = "RGBA(127,127,127,1)";
            context.shadowOffsetX = 3;
            context.shadowOffsetY = 3;
            context.shadowBlur = 0;
            context.fillStyle = "RGBA(0, 0, 0, 0.8)";
            context.fillText("Blur Canvas", 40, 80+hh);
             
            // section three - down shadow effect
            var hh = canvas.height/4 + hh;
            context.fillStyle="black";
            context.fillRect(0, hh, canvas.width, canvas.height/4);
            for(var i = 0; i < 10; i++)
            {
                context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")";
                context.shadowOffsetX = i*2;
                context.shadowOffsetY = i*2;
                context.shadowBlur = i*2;
                context.fillStyle = "RGBA(127, 127, 127, 1)";
                context.fillText("Blur Canvas", 40, 80+hh);
            }
             
            // section four -  fade effect
            var hh = canvas.height/4 + hh;
            context.fillStyle="green";
            context.fillRect(0, hh, canvas.width, canvas.height/4);
            for(var i = 0; i < 10; i++)
            {
                context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")";
                context.shadowOffsetX = 0;
                context.shadowOffsetY = -i*2;
                context.shadowBlur = i*2;
                context.fillStyle = "RGBA(127, 127, 127, 1)";
                context.fillText("Blur Canvas", 40, 80+hh);
            }
            for(var i = 0; i < 10; i++)
            {
                context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")";
                context.shadowOffsetX = 0;
                context.shadowOffsetY = i*2;
                context.shadowBlur = i*2;
                context.fillStyle = "RGBA(127, 127, 127, 1)";
                context.fillText("Blur Canvas", 40, 80+hh);
            }
            for(var i = 0; i < 10; i++)
            {
                context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")";
                context.shadowOffsetX = i*2;
                context.shadowOffsetY = 0;
                context.shadowBlur = i*2;
                context.fillStyle = "RGBA(127, 127, 127, 1)";
                context.fillText("Blur Canvas", 40, 80+hh);
            }
            for(var i = 0; i < 10; i++)
            {
                context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")";
                context.shadowOffsetX = -i*2;
                context.shadowOffsetY = 0;
                context.shadowBlur = i*2;
                context.fillStyle = "RGBA(127, 127, 127, 1)";
                context.fillText("Blur Canvas", 40, 80+hh);
            }
        }
         
    </script>
</head>
<body>
    <h1>HTML5 Canvas</h1>
    <pre>Fill And Stroke Clip</pre>
    <div id="my_painter">
        <canvas id="text_canvas"></canvas>
    </div>
</body>
</html>
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