HTML5 Canvas陰影用法演示 · HTML5 Canvas編程

**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： ![](https://box.kancloud.cn/2016-05-17_573adb378b81b.jpg) **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： ![](https://box.kancloud.cn/2016-05-17_573adb379e37c.jpg) 程序代碼： ~~~ <!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> ~~~ **轉載請注明**