首页
所有分类
TAGS
文字工具 EMOJI BIBLE
编程 Javascript

js canvas实现橡皮擦效果

Posted in Javascript onDecember 20, 2018

本文实例为大家分享了canvas实现橡皮擦效果的具体代码，供大家参考，具体内容如下

html部分

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html" charset="utf-8" />
<meta name="viewport" content="initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, user-scalable=no" /> 
<title>My Canvas 0.1</title>
<style type="text/css">
html,body,div,img{
 margin:0;
 padding:0;
}
a,a:hover{
 text-decoration:none;
}
.background{
 width:100%;
 position:fixed;
 top:0;
 left:0;
}
</style>
</head>
 
<body>
<img src="images/background.png" class="background resizeContainer"/>
<div id="J_cover" class="resizeContainer"></div>
<script type="text/javascript" src="js/zepto.js"></script>
<script type="text/javascript" src="js/lottery.js"></script>
<script type="text/javascript">
var canvas = {
 init : function(){
 var self = this;
 var node = document.getElementById('J_cover'),
 canvas_url = 'images/cover.png',
 type = 'image';
 
 var lottery = new Lottery(node, canvas_url, type, window_w, window_h, self.callback);
  lottery.init();
 },
 callback : function(){
 $('#J_cover').hide();
 }
}
var window_h, window_w;
$(document).ready(function(){
 window_w = $(window).width();
 window_h = $(window).height();
 
 $('.resizeContainer').width(window_w).height(window_h);
 
 canvas.init();
});
</script>
</body>
</html>

lottery.js

function Lottery(node, cover, coverType, width, height, drawPercentCallback) {
//node：canvas的id，cover：上面一层的图片地址，coverType：'image'or'color'，width：canvas宽, height：canvas高, drawPercentCallback：回调函数
 //canvas
 this.conNode = node;
 
 this.background = null;
 this.backCtx = null;
 
 this.mask = null;
 this.maskCtx = null;
 
 this.lottery = null;
 this.lotteryType = 'image';
 
 this.cover = cover || "#000";
 this.coverType = coverType;
 this.pixlesData = null;
 
 this.width = width;
 this.height = height;
 
 this.lastPosition = null;
 this.drawPercentCallback = drawPercentCallback;
 
 this.vail = false;
}
 
Lottery.prototype = {
 createElement: function(tagName, attributes) {
  var ele = document.createElement(tagName);
  for (var key in attributes) {
   ele.setAttribute(key, attributes[key]);
  }
  return ele;
 },
 
 getTransparentPercent: function(ctx, width, height) {
  var imgData = ctx.getImageData(0, 0, width, height),
   pixles = imgData.data,
   transPixs = [];
 
  for (var i = 0, j = pixles.length; i < j; i += 4) {
   var a = pixles[i + 3];
   if (a < 128) {
    transPixs.push(i);
   }
  }
  return (transPixs.length / (pixles.length / 4) * 100).toFixed(2);
 },
 
 resizeCanvas: function(canvas, width, height) {
  canvas.width = width;
  canvas.height = height;
  canvas.getContext('2d').clearRect(0, 0, width, height);
 },
 
 resizeCanvas_w: function(canvas, width, height) {
  canvas.width = width;
  canvas.height = height;
  canvas.getContext('2d').clearRect(0, 0, width, height);
 
  if (this.vail) this.drawLottery();
  else this.drawMask();
 },
 
 drawPoint: function(x, y, fresh) {
  this.maskCtx.beginPath();
  this.maskCtx.arc(x, y, 20, 0, Math.PI * 2);
  this.maskCtx.fill();
 
  this.maskCtx.beginPath();
 
  this.maskCtx.lineWidth = 60;
  this.maskCtx.lineCap = this.maskCtx.lineJoin = 'round';
 
  if (this.lastPosition) {
   this.maskCtx.moveTo(this.lastPosition[0], this.lastPosition[1]);
  }
  this.maskCtx.lineTo(x, y);
  this.maskCtx.stroke();
 
  this.lastPosition = [x, y];
 
  this.mask.style.zIndex = (this.mask.style.zIndex == 20) ? 21 : 20;
 },
 
 bindEvent: function() {
  var _this = this;
  var device = (/android|webos|iphone|ipad|ipod|blackberry|iemobile|opera mini/i.test(navigator.userAgent.toLowerCase()));
  var clickEvtName = device ? 'touchstart' : 'mousedown';
  var moveEvtName = device ? 'touchmove' : 'mousemove';
  if (!device) {
   var isMouseDown = false;
   _this.conNode.addEventListener('mouseup', function(e) {
    e.preventDefault();
 
    isMouseDown = false;
    var per = _this.getTransparentPercent(_this.maskCtx, _this.width, _this.height);
 
    if (per >= 80) {//在大于等于80%的时候调用回调函数
     if (typeof(_this.drawPercentCallback) == 'function') _this.drawPercentCallback();
    }
   }, false);
  } else {
   _this.conNode.addEventListener("touchmove", function(e) {
    if (isMouseDown) {
     e.preventDefault();
    }
    if (e.cancelable) {
     e.preventDefault();
    } else {
     window.event.returnValue = false;
    }
   }, false);
   _this.conNode.addEventListener('touchend', function(e) {
    isMouseDown = false;
    var per = _this.getTransparentPercent(_this.maskCtx, _this.width, _this.height);
    if (per >= 80) {//在大于等于80%的时候调用回调函数
     if (typeof(_this.drawPercentCallback) == 'function') _this.drawPercentCallback();
    }
   }, false);
  }
 
  this.mask.addEventListener(clickEvtName, function(e) {
   e.preventDefault();
 
   isMouseDown = true;
 
   var x = (device ? e.touches[0].pageX : e.pageX || e.x);
   var y = (device ? e.touches[0].pageY : e.pageY || e.y);
 
   _this.drawPoint(x, y, isMouseDown);
  }, false);
 
  this.mask.addEventListener(moveEvtName, function(e) {
   e.preventDefault();
 
   if (!isMouseDown) return false;
   e.preventDefault();
 
   var x = (device ? e.touches[0].pageX : e.pageX || e.x);
   var y = (device ? e.touches[0].pageY : e.pageY || e.y);
 
   _this.drawPoint(x, y, isMouseDown);
  }, false);
 },
 
 drawLottery: function() {
  if (this.lotteryType == 'image') {
   var image = new Image(),
    _this = this;
   image.onload = function() {
    this.width = _this.width;
    this.height = _this.height;
    _this.resizeCanvas(_this.background, _this.width, _this.height);
    _this.backCtx.drawImage(this, 0, 0, _this.width, _this.height);
    _this.drawMask();
   }
   image.src = this.lottery;
  } else if (this.lotteryType == 'text') {
   this.width = this.width;
   this.height = this.height;
   this.resizeCanvas(this.background, this.width, this.height);
   this.backCtx.save();
   this.backCtx.fillStyle = '#FFF';
   this.backCtx.fillRect(0, 0, this.width, this.height);
   this.backCtx.restore();
   this.backCtx.save();
   var fontSize = 30;
   this.backCtx.font = 'Bold ' + fontSize + 'px Arial';
   this.backCtx.textAlign = 'center';
   this.backCtx.fillStyle = '#F60';
   this.backCtx.fillText(this.lottery, this.width / 2, this.height / 2 + fontSize / 2);
   this.backCtx.restore();
   this.drawMask();
  }
 },
 
 drawMask: function() {
  if (this.coverType == 'color') {
   this.maskCtx.fillStyle = this.cover;
   this.maskCtx.fillRect(0, 0, this.width, this.height);
   this.maskCtx.globalCompositeOperation = 'destination-out';
  } else if (this.coverType == 'image') {
   var image = new Image(),
    _this = this;
   image.onload = function() {
    _this.resizeCanvas(_this.mask, _this.width, _this.height);
 
    var android = (/android/i.test(navigator.userAgent.toLowerCase()));
 
    _this.maskCtx.globalAlpha = 1;//上面一层的透明度，1为不透明
    _this.maskCtx.drawImage(this, 0, 0, this.width, this.height, 0, 0, _this.width, _this.height);
 
    //---以下一段为在上面一层上写字
    // var fontSize = 50;
    // var txt = '123123';
    // var gradient = _this.maskCtx.createLinearGradient(0, 0, _this.width, 0);
    // gradient.addColorStop("0", "#fff");
    // gradient.addColorStop("1.0", "#000");
 
    // _this.maskCtx.font = 'Bold ' + fontSize + 'px Arial';
    // _this.maskCtx.textAlign = 'left';
    // _this.maskCtx.fillStyle = gradient;
    // _this.maskCtx.fillText(txt, _this.width / 2 - _this.maskCtx.measureText(txt).width / 2, 100);
 
    // _this.maskCtx.globalAlpha = 1;
 
    _this.maskCtx.globalCompositeOperation = 'destination-out';
   }
   image.src = this.cover;
  }
 },
 
 init: function(lottery, lotteryType) {
  if (lottery) {
   this.lottery = lottery;
   this.lottery.width = this.width;
   this.lottery.height = this.height;
   this.lotteryType = lotteryType || 'image';
 
   this.vail = true;
  }
  if (this.vail) {
   this.background = this.background || this.createElement('canvas', {
    style: 'position:fixed;top:0;left:0;background-color:transparent;'
   });
  }
 
  this.mask = this.mask || this.createElement('canvas', {
   style: 'position:fixed;top:0;left:0;background-color:transparent;'
  });
  this.mask.style.zIndex = 20;
 
  if (!this.conNode.innerHTML.replace(/[\w\W]| /g, '')) {
   if (this.vail) this.conNode.appendChild(this.background);
   this.conNode.appendChild(this.mask);
   this.bindEvent();
  }
  if (this.vail) this.backCtx = this.backCtx || this.background.getContext('2d');
  this.maskCtx = this.maskCtx || this.mask.getContext('2d');
 
  if (this.vail) this.drawLottery();
  else this.drawMask();
 
  var _this = this;
  window.addEventListener('resize', function() {
   _this.width = document.documentElement.clientWidth;
   _this.height = document.documentElement.clientHeight;
 
   _this.resizeCanvas_w(_this.mask, _this.width, _this.height);
  }, false);
 }
}

另一个zepto.js是库函数文件，可网上自行查找

出来的效果如图

js canvas实现橡皮擦效果

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持三水点靠木。

js canvas实现橡皮擦效果

- Author -

snow_finland

声明：登载此文出于传递更多信息之目的，并不意味着赞同其观点或证实其描述。

Javascript 相关文章推荐
GRID拖拽行的实例代码
Jul 18 Javascript
原生js做的手风琴效果的导航菜单
Nov 08 Javascript
让jQuery Mobile不显示讨厌loading界面的方法
Feb 19 Javascript
js触发select onchange事件的小技巧
Aug 05 Javascript
jQuery不兼容input的change事件问题解决过程
Dec 05 Javascript
JS拖动鼠标画出方框实现鼠标选区的方法
Aug 05 Javascript
vue项目引入字体.ttf的方法
Sep 28 Javascript
js实现点击展开隐藏效果（实例代码）
Sep 28 Javascript
js 判断当前时间是否处于某个一个时间段内
Sep 19 Javascript
vue 动态表单开发方法案例详解
Dec 02 Javascript
Vue使用路由钩子拦截器beforeEach和afterEach监听路由
Nov 16 Javascript
JavaScript实现点击切换验证码及校验
Jan 10 Javascript
浅谈VueJS SSR 后端绘制内存泄漏的相关解决经验
Dec 20 #Javascript
Cocos2d实现刮刮卡效果
Dec 20 #Javascript
浅谈Fetch 数据交互方式
Dec 20 #Javascript
cocos2dx+lua实现橡皮擦功能
Dec 20 #Javascript
element-ui table span-method(行合并)的实现代码
Dec 20 #Javascript
fetch 如何实现请求数据
Dec 20 #Javascript
JS闭包经典实例详解
Dec 20 #Javascript
人人对战(1) 算法(1) 双人对弈(1) OVERLORD(1) Vscode(3) 数据表(1) 后端(1) 时钟(1) 2022年7月新番(1) SSH(3)
You might like
最省空间的计数器
2006/10/09 PHP
Ext.data.PagingMemoryProxy分页一次性读取数据的实现代码
2010/04/07 PHP
php Smarty初体验二 获取配置信息
2011/08/08 PHP
php+redis消息队列实现抢购功能
2018/02/08 PHP
基于PHP的微信公众号的开发流程详解
2020/08/07 PHP
jQuery Dialog 弹出层对话框插件
2010/08/09 Javascript
纯JAVASCRIPT图表动画插件Highcharts Examples
2011/04/16 Javascript
关于setInterval、setTimeout在jQuery中的使用注意事项
2011/09/28 Javascript
Javascript获取窗口(容器)的大小及位置参数列举及简要说明
2012/12/09 Javascript
js判断浏览器类型的方法
2013/08/07 Javascript
JS仿Windows开机启动Loading进度条的方法
2015/02/26 Javascript
js实现无缝滚动特效
2015/12/20 Javascript
jQuery给元素添加样式的方法详解
2015/12/30 Javascript
jQuery中的一些常见方法小结(推荐)
2016/06/13 Javascript
jquery.Jcrop结合JAVA后台实现图片裁剪上传实例
2016/11/05 Javascript
JavaScript模板引擎Template.js使用详解
2016/12/15 Javascript
微信小程序 页面之间传参实例详解
2017/01/13 Javascript
vue 数组和对象不能直接赋值情况和解决方法(推荐)
2017/10/25 Javascript
Vue2 配置 Axios api 接口调用文件的方法
2017/11/13 Javascript
javaScript强制保留两位小数的输入数校验和小数保留问题
2018/05/09 Javascript
使用NestJS开发Node.js应用的方法
2018/12/03 Javascript
vue使用pdfjs显示PDF可复制的实现方法
2018/12/14 Javascript
JS数组方法shift()、unshift()用法实例分析
2020/01/18 Javascript
使用python实现正则匹配检索远端FTP目录下的文件
2015/03/25 Python
使用Python的Twisted框架实现一个简单的服务器
2015/04/16 Python
python模块之sys模块和序列化模块(实例讲解)
2017/09/13 Python
Python中property属性实例解析
2018/02/10 Python
对python读取CT医学图像的实例详解
2019/01/24 Python
pytorch中的transforms模块实例详解
2019/12/31 Python
小学语文业务学习材料
2014/06/02 职场文书
化工专业求职信
2014/07/01 职场文书
房屋租赁合同协议书范本
2014/10/19 职场文书
高校自主招生自荐信2015
2015/03/04 职场文书
国庆阅兵观后感
2015/06/15 职场文书
七年级作文（600字3篇）
2019/09/24 职场文书
Vue操作Storage本地化存储
2022/04/29 Vue.js