JavaScript html5 canvas画布中删除一个块区域的方法

2019-11-20 10:41:17

字体：大中小

来源：转载

供稿：网友

本文实例讲述了html5 canvas画布中删除一个块区域的方法。分享给大家供大家参考，具体如下：

运行效果截图如下：

附:图中，黑色小方块即为删除掉的块区域

具体代码如下：

index.html：

<!DOCTYPE html><html> <head>  <meta http-equiv="Content-type" content="text/html;charset=UTF-8" />  <title>canvas中删除一块区域</title>  <style type="text/css">   #canvas {    background:black; margin-top:100px; margin-left:200px;   }  </style> </head> <body>  <canvas id="canvas" width="500px" height="500px" ></canvas> </body> <script type="text/javascript" src="canvas.js"></script> <script type="text/javascript">  cache = {};  var offsetX = 50,   offsetY = 20;  cache.context = dyl.createContext('canvas');  dyl.rect(dyl.createColor(), 150, 150, 200, 200, 0.5);  for(var i=0; i<10; i++) {   dyl.clearRect(150 + i*20, 150 + i*20, 20, 20);  } </script></html>

canvas.js：

(function() {  var dyl = {cache: {}};  dyl.setContext = function(context) {    dyl.cache._context = context;    return context;  };  dyl.getDom = function(id) {    return document.getElementById(id);  };  dyl._getContext = function() {    return dyl.cache._context;  };  dyl.save = function() {    var context = dyl._getContext();    context ? context.save() : void(0);  };  dyl.restore = function() {    var context = dyl._getContext();    context ? context.restore() : void(0);  };  dyl.createContext = function(canvasID) {    var canvas = this.getDom(canvasID);    if(!canvas) {      return null;    }    return dyl.setContext(canvas.getContext("2d"));  };  dyl.createColor = function() {    var color = "rgb(";    color += Math.round(Math.random()*255);    color += ",";    color += Math.round(Math.random()*255);    color += ",";    color += Math.round(Math.random()*255);    color += ")";    return color;  };  dyl.addImg = function(img, x, y) {    var context = dyl._getContext();    if(!img || !context) {      return;    }    if(typeof img === "string") {      var oImg = new Image();      oImg.src = img;      oImg.onload = function() {        context.drawImage(oImg, x, y);      }      return;    }     context.drawImage(img, x, y);  };  dyl.rect = function(color, x, y, width, height, alpha) {    var context = dyl._getContext();    if(!context) {      return;    }    context.save();    context.fillStyle = color;    context.globalAlpha = alpha ? alpha : 1;    context.fillRect(x, y, width, height);    context.restore();  };  dyl.circle = function(color, x, y, r, alpha) {    var context = dyl._getContext();    context.save();    context.fillStyle = color;    context.beginPath();    context.globalAlpha = alpha ? alpha : 1;    context.arc(x, y, r, 0, 2*Math.PI);    context.fill();    context.stroke();  };  dyl.clearRect = function(x, y, width, height) {    var context = dyl._getContext();    if(!context) {      return;    }    context.clearRect(x, y, width, height);  };  dyl.scale = function(x, y) {    var context = dyl._getContext();    if(!context) {      return;    }    x = x ? x : 1;    y = y ? y : 1;    context.scale(x, y);  };  if(!window.dyl) {    window.dyl = dyl;  }})();

希望本文所述对大家JavaScript程序设计有所帮助。

上一篇：AngualrJS中每次$http请求时的一个遮罩层Directive

下一篇：HTML5游戏引擎LTweenLite实现的超帅动画效果(附demo源码下载)