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。
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