HTML5 Canvas阴影使用方法实例演示_html5教程技巧

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:

<script> <br />var ctx = null; // global variable 2d context <br />var imageTexture = null; <br />window.onload = function() { <br />var canvas = document.getElementById("text_canvas"); <br />console.log(canvas.parentNode.clientWidth); <br />canvas.width = canvas.parentNode.clientWidth; <br />canvas.height = canvas.parentNode.clientHeight; <br />if (!canvas.getContext) { <br />console.log("Canvas not supported. Please install a HTML5 compatible browser."); <br />return; <br />} <br />var context = canvas.getContext('2d'); <br />// section one - shadow and blur <br />context.fillStyle="black"; <br />context.fillRect(0, 0, canvas.width, canvas.height/4); <br />context.font = '60pt Calibri'; <br />context.shadowColor = "white"; <br />context.shadowOffsetX = 0; <br />context.shadowOffsetY = 0; <br />context.shadowBlur = 20; <br />context.fillText("Blur Canvas", 40, 80); <br />context.strokeStyle = "RGBA(0, 255, 0, 1)"; <br />context.lineWidth = 2; <br />context.strokeText("Blur Canvas", 40, 80); <br />// section two - shadow font <br />var hh = canvas.height/4; <br />context.fillStyle="white"; <br />context.fillRect(0, hh, canvas.width, canvas.height/4); <br />context.font = '60pt Calibri'; <br />context.shadowColor = "RGBA(127,127,127,1)"; <br />context.shadowOffsetX = 3; <br />context.shadowOffsetY = 3; <br />context.shadowBlur = 0; <br />context.fillStyle = "RGBA(0, 0, 0, 0.8)"; <br />context.fillText("Blur Canvas", 40, 80+hh); <br />// section three - down shadow effect <br />var hh = canvas.height/4 + hh; <br />context.fillStyle="black"; <br />context.fillRect(0, hh, canvas.width, canvas.height/4); <br />for(var i = 0; i < 10; i++) <br />{ <br />context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")"; <br />context.shadowOffsetX = i*2; <br />context.shadowOffsetY = i*2; <br />context.shadowBlur = i*2; <br />context.fillStyle = "RGBA(127, 127, 127, 1)"; <br />context.fillText("Blur Canvas", 40, 80+hh); <br />} <br />// section four - fade effect <br />var hh = canvas.height/4 + hh; <br />context.fillStyle="green"; <br />context.fillRect(0, hh, canvas.width, canvas.height/4); <br />for(var i = 0; i < 10; i++) <br />{ <br />context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")"; <br />context.shadowOffsetX = 0; <br />context.shadowOffsetY = -i*2; <br />context.shadowBlur = i*2; <br />context.fillStyle = "RGBA(127, 127, 127, 1)"; <br />context.fillText("Blur Canvas", 40, 80+hh); <br />} <br />for(var i = 0; i < 10; i++) <br />{ <br />context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")"; <br />context.shadowOffsetX = 0; <br />context.shadowOffsetY = i*2; <br />context.shadowBlur = i*2; <br />context.fillStyle = "RGBA(127, 127, 127, 1)"; <br />context.fillText("Blur Canvas", 40, 80+hh); <br />} <br />for(var i = 0; i < 10; i++) <br />{ <br />context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")"; <br />context.shadowOffsetX = i*2; <br />context.shadowOffsetY = 0; <br />context.shadowBlur = i*2; <br />context.fillStyle = "RGBA(127, 127, 127, 1)"; <br />context.fillText("Blur Canvas", 40, 80+hh); <br />} <br />for(var i = 0; i < 10; i++) <br />{ <br />context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")"; <br />context.shadowOffsetX = -i*2; <br />context.shadowOffsetY = 0; <br />context.shadowBlur = i*2; <br />context.fillStyle = "RGBA(127, 127, 127, 1)"; <br />context.fillText("Blur Canvas", 40, 80+hh); <br />} <br />} <br /></script>

HTML5 Canvas Clip Demo - By Gloomy Fish

Fill And Stroke Clip