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HTML5 Canvas陰影用法演示
HTML5 Canvas中提供了設置陰影的四個屬性值分別為：
context.shadowColor = “red” 表示設置陰影顏色為紅色
context.shadowOffsetX = 0表示陰影相對TEXT的水平距離，0表示兩者水平位置重合
context.shadowOffsetY = 0表示陰影相對TEXT的垂直距離，0表示兩者垂直位置重合
context.shadowBlur = 10 陰影模糊效果，值越大模糊越厲害。
一個最簡單的帶有陰影的矩形代碼如下：
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：
陰影文字：
只要設置shadowOffsetX與shadowOffsetY的值，當值都正數時，陰影相對文字的右下
方偏移。當值都為負數時，陰影相對文字的左上方偏移。
3D拉影效果：
在同一位置不斷的重復繪制文字同時改變shadowOffsetX、shadowOffsetY、shadowBlur
的值，從小到大不斷偏移不斷增加，透明度也不斷增加。就得到了拉影效果文字。
邊緣模糊效果文字：
在3D拉影效果的基礎上在四個方向重復，就得到了邊緣羽化的文字效果。
運行效果：
<!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> <h2>HTML5 Canvas Clip Demo - By Gloomy Fish</h2> <pre>Fill And Stroke Clip</pre> <div id="my_painter"> <canvas id="text_canvas"></canvas> </div> </body> </html>轉載請注明免責聲明：本站發布的內容（圖片、視頻和文字）以原創、轉載和分享為主，文章觀點不代表本網站立場，如果涉及侵權請聯系站長郵箱：is@yisu.com進行舉報，并提供相關證據，一經查實，將立刻刪除涉嫌侵權內容。
