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    HTML5 Canvas阴影使用方法实例演示
    POST TIME:2021-10-16 23:36
    HTML5 Canvas中提供了设置阴影的四个属性值分别为:
    context.shadowColor = “red” 表示设置阴影颜色为红色
    context.shadowOffsetX = 0表示阴影相对TEXT的水平距离,0表示两者水平位置重合
    context.shadowOffsetY = 0表示阴影相对TEXT的垂直距离,0表示两者垂直位置重合
    context.shadowBlur = 10 阴影模糊效果,值越大模糊越厉害。
    一个最简单的带有阴影的矩形代码如下:
    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.fillRect(10, hh+10, 200,canvas.height/4-20);
    效果如下:
     
    阴影文字:
    只要设置shadowOffsetX与shadowOffsetY的值,当值都正数时,阴影相对文字的右下
    方偏移。当值都为负数时,阴影相对文字的左上方偏移。
    3D拉影效果:
    在同一位置不断的重复绘制文字同时改变shadowOffsetX、shadowOffsetY、shadowBlur
    的值,从小到大不断偏移不断增加,透明度也不断增加。就得到了拉影效果文字。
    边缘模糊效果文字:
    在3D拉影效果的基础上在四个方向重复,就得到了边缘羽化的文字效果。
    运行效果:
     
    序代码:

    复制代码
    代码如下:

    <!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 Clip Demo - By Gloomy Fish</h1>
    <pre>Fill And Stroke Clip</pre>
    <div id="my_painter">
    <canvas id="text_canvas"></canvas>
    </div>
    </body>
    </html>
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