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纯CSS模拟刮奖效果
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<style>
*{
margin: 0;
padding: 0;
} p {
position: fixed;
top: 60%;
left: 0;
right: 0;
text-align: center;
transform: translateY(-50%);
font-size: 40px;
font-weight: 900;
color: white;
text-shadow: 0 0 50px black;
text-transform: capitalize;
font-family: 'Roboto','Helvetica','Arial',sans-serif;
letter-spacing: 5px;
} .box{
margin: 80px;
position: relative;
width: 300px;
height: 180px;
left: 460px;
}
#canvas{
position: absolute;
top: 0;
left: 0;
z-index: 5;
}
.bk{
width: 300px;
height: 180px;
background: #fff;
position: absolute;
top: 0;
left: 0;
text-align: center;
line-height: 180px;
}
#freshBtn{
margin-left: 660px;
user-select: none;
background: #ddd;
width: 80px;
height: 40px;
text-align: center;
line-height: 40px;
}
</style>
<body>
<p>Gary</p>
<div class="box">
<div class="bk">
一等奖
</div>
<canvas id="canvas"></canvas>
</div>
<div id="freshBtn">重置</div>
</body>
<script src="./js/canvas.js"></script>
<script>
var canvas = new canvasInit({
id: 'canvas',
text: '刮开抽奖',
cover: '#1f1f1f',
coverType: 'color',
width: 300,
height: 180,
drawPercentCallback: (num) => {
if(num > 30) {
alert('恭喜获得一等奖')
canvas.fresh() // 重置
}
}
})
</script>
</html>
index.html
class canvasClass {
constructor (id,text,cover,coverType,width,height,drawPercentCallback) {
this.conId = id; /*canvasID */
this.conNode = document.getElementById(this.conId);
this.ctx = this.conNode.getContext('2d');
this.coverText = text;
this.cover = cover; /**图层颜色或图片 */
this.coverType = coverType; /**图层类型（image/color） */
this.width = width;
this.height = height;
this.drawPercentCallback = drawPercentCallback
this.clientRect = null;
this.isMouseDown = false;
}
/**
* 绘制canvas
*/
fillCanvas () {
this.conNode.setAttribute('width', this.width);
this.conNode.setAttribute('height', this.height);
if (this.coverType == 'color') {
this.ctx.save();
this.ctx.fillStyle = this.cover;
this.ctx.fillRect(0, 0, this.width, this.height);
this.ctx.restore();
this.ctx.save();
var fontSize = 30;
this.ctx.font = '30px Arial';
this.ctx.textAlign = 'center';
this.ctx.fillStyle = '#fff';
this.ctx.fillText(this.coverText, this.width/2, this.height/2+fontSize/2);
this.ctx.restore();
this.ctx.globalCompositeOperation = 'destination-out';
} else if (this.coverType == 'image') {
var image = new Image(this.width, this.height)
image.onload = () => {
this.ctx.drawImage(image, 0, 0, this.width, this.height);
}
image.src = this.cover;
}
this.clientRect = this.conNode ? this.conNode.getBoundingClientRect() : null
}
/**
* 事件监听
*/
bindEvent () {
/**移动端检测 */
var device = (/android|webos|iphone|ipad|ipod|blackberry|iemobile|opera mini/i.test(navigator.userAgent.toLowerCase()));
var clickEvt = device ? 'touchstart' : 'mousedown';
var moveEvt = device ? 'touchmove' : 'mousemove';
var x1,y1,x2,y2;
if (!device) {
document.addEventListener('mouseup', (e) => {
this.isMouseDown = false;
})
} else {
document.addEventListener("touchmove", (e) => {
if (this.isMouseDown) {
e.preventDefault();
}
})
document.addEventListener("touchend", (e) => {
this.isMouseDown = false;
})
}
/**添加监听 */
this.conNode.addEventListener(clickEvt, (e) => {
this.isMouseDown = true;
x1 = device ? e.touches[0].offsetX : e.offsetX;
y1 = device ? e.touches[0].offsetY : e.offsetY;
this.drawPoint(x1, y1)
})
this.conNode.addEventListener(moveEvt, (e) => {
if (!device && !this.isMouseDown) {
return false;
}
this.isMouseDown = true;
x2 = device ? e.touches[0].offsetX : e.offsetX;
y2 = device ? e.touches[0].offsetY : e.offsetY;
this.drawPoint(x1, y1, x2, y2)
// console.log(x1,x2,y1,y2)
x1 = x2
y1 = y2
// [x1, y1] = [x2, y2]
})
}
/**
* 抹去， 返回百分比
*/
drawPoint (x1, y1, x2, y2) {
var bar = 20; // 半径
this.ctx.beginPath();
if (x2) {
/**
* 优化绘制路径
*/
var asin = bar*Math.sin(Math.atan((y2-y1)/(x2-x1)));
var acos = bar*Math.cos(Math.atan((y2-y1)/(x2-x1)))
var x3 = x1+asin;
var y3 = y1-acos;
var x4 = x1-asin;
var y4 = y1+acos;
var x5 = x2+asin;
var y5 = y2-acos;
var x6 = x2-asin;
var y6 = y2+acos;
this.ctx.save();
this.ctx.beginPath();
this.ctx.moveTo(x3,y3);
this.ctx.lineTo(x5,y5);
this.ctx.lineTo(x6,y6);
this.ctx.lineTo(x4,y4);
this.ctx.closePath();
this.ctx.clip();
this.ctx.clearRect(0,0,this.width,this.height);
this.ctx.restore();
this.ctx.arc(x2, y2, bar, 0, Math.PI*2, true);
} else {
this.ctx.arc(x1, y1, bar, 0, Math.PI*2, true);
}
this.ctx.fill();
if (this.drawPercentCallback) {
this.drawPercentCallback(this.getTransparentPercent());
}
}
getTransparentPercent () {
var imgData = this.ctx.getImageData(0, 0, this.width, this.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);
}
}
function canvasInit(json) {
var arr = []
for (let item in json) {
arr.push(json[item])
}
this.init = new canvasClass(...arr)
this.init.fillCanvas()
this.init.bindEvent()
var btn = document.querySelector('#freshBtn');
btn.addEventListener('click', (e) => {
this.init.fillCanvas()
});
}
canvasInit.prototype.fresh = function () {
console.log(this.init)
this.init.fillCanvas()
this.init.isMouseDown = false
}canvas.css
（直接复制就可以使用了O(∩_∩)O~ ES6编写）
=>是es6语法中的arrow function(箭头函数)
举例：
(x) => x + 6
相当于
function(x){
return x + 6;
}
实现过程
CSS
画板.class
class canvasClass {
constructor (id,text,cover,coverType,width,height,drawPercentCallback) {
this.conId = id; /*canvasID */
this.conNode = document.getElementById(this.conId);
this.ctx = this.conNode.getContext('2d');
this.coverText = text;
this.cover = cover; /**图层颜色或图片 */
this.coverType = coverType; /**图层类型（image/color） */
this.width = width;
this.height = height;
this.drawPercentCallback = drawPercentCallback
this.clientRect = null;
this.isMouseDown = false;
}
/**
* 绘制canvas
*/
fillCanvas () {
this.conNode.setAttribute('width', this.width);
this.conNode.setAttribute('height', this.height);
if (this.coverType == 'color') {
this.ctx.save();
this.ctx.fillStyle = this.cover;
this.ctx.fillRect(0, 0, this.width, this.height);
this.ctx.restore();
this.ctx.save();
var fontSize = 30;
this.ctx.font = '30px Arial';
this.ctx.textAlign = 'center';
this.ctx.fillStyle = '#fff';
this.ctx.fillText(this.coverText, this.width/2, this.height/2+fontSize/2);
this.ctx.restore();
this.ctx.globalCompositeOperation = 'destination-out';
} else if (this.coverType == 'image') {
var image = new Image(this.width, this.height)
image.onload = () => {
this.ctx.drawImage(image, 0, 0, this.width, this.height);
}
image.src = this.cover;
}
this.clientRect = this.conNode ? this.conNode.getBoundingClientRect() : null
}
/**
* 事件监听
*/
bindEvent () {
/**移动端检测 */
var device = (/android|webos|iphone|ipad|ipod|blackberry|iemobile|opera mini/i.test(navigator.userAgent.toLowerCase()));
var clickEvt = device ? 'touchstart' : 'mousedown';
var moveEvt = device ? 'touchmove' : 'mousemove';
var x1,y1,x2,y2;
if (!device) {
document.addEventListener('mouseup', (e) => {
this.isMouseDown = false;
})
} else {
document.addEventListener("touchmove", (e) => {
if (this.isMouseDown) {
e.preventDefault();
}
})
document.addEventListener("touchend", (e) => {
this.isMouseDown = false;
})
}
/**添加监听 */
this.conNode.addEventListener(clickEvt, (e) => {
this.isMouseDown = true;
x1 = device ? e.touches[0].offsetX : e.offsetX;
y1 = device ? e.touches[0].offsetY : e.offsetY;
this.drawPoint(x1, y1)
})
this.conNode.addEventListener(moveEvt, (e) => {
if (!device && !this.isMouseDown) {
return false;
}
this.isMouseDown = true;
x2 = device ? e.touches[0].offsetX : e.offsetX;
y2 = device ? e.touches[0].offsetY : e.offsetY;
this.drawPoint(x1, y1, x2, y2)
// console.log(x1,x2,y1,y2)
x1 = x2
y1 = y2
// [x1, y1] = [x2, y2]
})
}
/**
* 抹去， 返回百分比
*/
drawPoint (x1, y1, x2, y2) {
var bar = 20; // 半径
this.ctx.beginPath();
if (x2) {
/**
* 优化绘制路径
*/
var asin = bar*Math.sin(Math.atan((y2-y1)/(x2-x1)));
var acos = bar*Math.cos(Math.atan((y2-y1)/(x2-x1)))
var x3 = x1+asin;
var y3 = y1-acos;
var x4 = x1-asin;
var y4 = y1+acos;
var x5 = x2+asin;
var y5 = y2-acos;
var x6 = x2-asin;
var y6 = y2+acos;
this.ctx.save();
this.ctx.beginPath();
this.ctx.moveTo(x3,y3);
this.ctx.lineTo(x5,y5);
this.ctx.lineTo(x6,y6);
this.ctx.lineTo(x4,y4);
this.ctx.closePath();
this.ctx.clip();
this.ctx.clearRect(0,0,this.width,this.height);
this.ctx.restore();
this.ctx.arc(x2, y2, bar, 0, Math.PI*2, true);
} else {
this.ctx.arc(x1, y1, bar, 0, Math.PI*2, true);
}
this.ctx.fill();
if (this.drawPercentCallback) {
this.drawPercentCallback(this.getTransparentPercent());
}
}
getTransparentPercent () {
var imgData = this.ctx.getImageData(0, 0, this.width, this.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);
}
}class canvasClass
1、绘制canvas画布
2、添加事件监听
3、刮奖效果
构造函数省略...
1、绘制canvas画布
fillCanvas () {
this.conNode.setAttribute('width', this.width);
this.conNode.setAttribute('height', this.height);
if (this.coverType == 'color') {
this.ctx.save();
this.ctx.fillStyle = this.cover;
this.ctx.fillRect(0, 0, this.width, this.height);
this.ctx.restore();
this.ctx.save();
var fontSize = 30;
this.ctx.font = '30px Arial';
this.ctx.textAlign = 'center';
this.ctx.fillStyle = '#fff';
this.ctx.fillText(this.coverText, this.width/2, this.height/2+fontSize/2);
this.ctx.restore();
this.ctx.globalCompositeOperation = 'destination-out';
} else if (this.coverType == 'image') {
var image = new Image(this.width, this.height)
image.onload = () => {
this.ctx.drawImage(image, 0, 0, this.width, this.height);
}
image.src = this.cover;
}
this.clientRect = this.conNode ? this.conNode.getBoundingClientRect() : null
}2、添加事件监听
bindEvent () {
/**移动端检测 */
var device = (/android|webos|iphone|ipad|ipod|blackberry|iemobile|opera mini/i.test(navigator.userAgent.toLowerCase()));
var clickEvt = device ? 'touchstart' : 'mousedown';
var moveEvt = device ? 'touchmove' : 'mousemove';
var x1,y1,x2,y2;
if (!device) {
document.addEventListener('mouseup', (e) => {
this.isMouseDown = false;
})
} else {
document.addEventListener("touchmove", (e) => {
if (this.isMouseDown) {
e.preventDefault();
}
})
document.addEventListener("touchend", (e) => {
this.isMouseDown = false;
})
}
/**添加监听 */
this.conNode.addEventListener(clickEvt, (e) => {
this.isMouseDown = true;
x1 = device ? e.touches[0].offsetX : e.offsetX;
y1 = device ? e.touches[0].offsetY : e.offsetY;
this.drawPoint(x1, y1)
})
this.conNode.addEventListener(moveEvt, (e) => {
if (!device && !this.isMouseDown) {
return false;
}
this.isMouseDown = true;
x2 = device ? e.touches[0].offsetX : e.offsetX;
y2 = device ? e.touches[0].offsetY : e.offsetY;
this.drawPoint(x1, y1, x2, y2)
// console.log(x1,x2,y1,y2)
x1 = x2
y1 = y2
// [x1, y1] = [x2, y2]
})
}3、刮奖效果
drawPoint (x1, y1, x2, y2) {
var bar = 20; // 半径
this.ctx.beginPath();
if (x2) {
/**
* 优化绘制路径
*/
var asin = bar*Math.sin(Math.atan((y2-y1)/(x2-x1)));
var acos = bar*Math.cos(Math.atan((y2-y1)/(x2-x1)))
var x3 = x1+asin;
var y3 = y1-acos;
var x4 = x1-asin;
var y4 = y1+acos;
var x5 = x2+asin;
var y5 = y2-acos;
var x6 = x2-asin;
var y6 = y2+acos;
this.ctx.save();
this.ctx.beginPath();
this.ctx.moveTo(x3,y3);
this.ctx.lineTo(x5,y5);
this.ctx.lineTo(x6,y6);
this.ctx.lineTo(x4,y4);
this.ctx.closePath();
this.ctx.clip();
this.ctx.clearRect(0,0,this.width,this.height);
this.ctx.restore();
this.ctx.arc(x2, y2, bar, 0, Math.PI*2, true);
} else {
this.ctx.arc(x1, y1, bar, 0, Math.PI*2, true);
}
this.ctx.fill();
if (this.drawPercentCallback) {
this.drawPercentCallback(this.getTransparentPercent());
}
}初始化canvas.class画布
function canvasInit(json) {
var arr = []
for (let item in json) {
arr.push(json[item])
}
this.init = new canvasClass(...arr)
this.init.fillCanvas()
this.init.bindEvent()
var btn = document.querySelector('#freshBtn');
btn.addEventListener('click', (e) => {
this.init.fillCanvas()
});
}按钮
#freshBtn{
margin-left: 660px;
user-select: none;
background: #ddd;
width: 80px;
height: 40px;
text-align: center;
line-height: 40px;
}刮奖区域
.box{
margin: 80px;
position: relative;
width: 300px;
height: 180px;
left: 460px;
}DOM
设置文档内容和显示文本
<div class="box">
<div class="bk">
一等奖
</div>
<canvas id="canvas"></canvas>
</div>
<div id="freshBtn">重置</div>
模拟抽奖效果时bk中文字可以用随机
给canvas.class画布传参
<script>
var canvas = new canvasInit({
id: 'canvas',
text: '刮开抽奖',
cover: '#1f1f1f',
coverType: 'color',
width: 300,
height: 180,
drawPercentCallback: (num) => {
if(num > 30) {
alert('恭喜获得一等奖')
canvas.fresh() // 重置
}
}
})
</script>