js canvas实现滑块验证

<template>
 <div class="sliderContent">
 <div class="imgDev" :style="'width:' + width + 'px;'">
 <canvas :id="id" :width="width" :height="height"></canvas>
 <canvas
 class="slider"
 :id="id + 'sliderBlock'"
 :width="width"
 :height="height"
 :style="'left:' + sliderLeft + 'px;'"
 ></canvas>
 </div>
 <div class="moveSLider" :style="'width:' + width + 'px'">
 <div class="react" @mousedown.stop="moveBall($event)">
 <div
 class="yuan"
 :style="'left:' + (sliderLeft + 10) + 'px;'"
 ></div>
 </div>
 </div>
 </div>
</template>

<script>
export default {
 data() {
 return {
 width: 200,//盒子的宽度
 height: 200,//盒子的高度，当设置图片原比例显示的时候这个参数就不好使了
 id: new Date().getTime(),
 r: 9, //半圆的半径
 w: 40, //滑块的宽度
 imgOriginalScale: true, //图片是否显示原来比例
 sliderLeft: 0,//滑块的初始位置
 rangeValue:4,//当滑块到什么范围内算正确
 imgsrc:require("../assets/img/ver-2.png")//引入你想要的背景图片
 };
 },
 mounted() {
 this.init();
 },
 methods: {
 init() {
 this.loadImage();
 },
 loadImage() {//加载图片
 let mainDom = document.getElementById(this.id);
 let bg = mainDom.getContext("2d");
 let blockDom = document.getElementById(this.id + "sliderBlock");
 let block = blockDom.getContext("2d");
 let imgsrc = this.imgsrc;
 let img = document.createElement("img");
 img.style.objectFit = "scale-down";
 img.src = imgsrc;
 img.onload = () => {
 if (this.imgOriginalScale) {
 //根据图片的尺寸变化计算一下图片原来的比例
 mainDom.height = (img.height / img.width) * mainDom.width;
 blockDom.height = (img.height / img.width) * blockDom.width;
 }
 bg.drawImage(img, 0, 0, mainDom.width, mainDom.height);
 this.drawBlock(bg, mainDom.width, mainDom.height, "fill"); //绘制滑块部分
 this.drawBlock(block, blockDom.width, blockDom.height, "clip", img); //绘制滑块部分 这里注意一定要先剪裁然后在绘制图片(这里图片要传进去不然没有办法控制)
 };
 },
 drawBlock(ctx, width, height, type, img) {//这里是二合一函数，可以画出阴影部分也切割出拼图形状的函数
 let { w, r, sliderLeft } = this;
 //这地方用随机数每次显示的位置都不同
 var x = this.random(30, width - w - r - 1); //这里最大值为了不让滑块进入隐藏所以要减去滑块的宽度 有个半圆所以要减去半圆位置
 var y = this.random(10, height - w - r - 1);
 if (type == "clip") {//这里要保证在两个东西要在同一个y值上
 x = sliderLeft;
 y = this.y;
 } else {
 this.x = x;
 this.y = y;
 }
 let PI = Math.PI;
 //绘制
 ctx.beginPath();
 //left
 ctx.moveTo(x, y);
 //top
 ctx.arc(x + (w + 5) / 2, y, r, -PI, 0, true);
 ctx.lineTo(x + w + 5, y);
 //right
 ctx.arc(x + w + 5, y + w / 2, r, 1.5 * PI, 0.5 * PI, false);
 ctx.lineTo(x + w + 5, y + w);
 //bottom
 ctx.arc(x + (w + 5) / 2, y + w, r, 0, PI, false);
 ctx.lineTo(x, y + w);
 ctx.arc(x, y + w / 2, r, 0.5 * PI, 1.5 * PI, true);
 ctx.lineTo(x, y);
 if (type == "clip") {
 ctx.shadowBlur = 10;
 ctx.shadowColor = "black";
 }
 ctx.lineWidth = 1;
 ctx.fillStyle = "rgba(0, 0, 0, 0.4)"; //设置背景颜色
 ctx.stroke();
 ctx[type]();
 if (img) {
 ctx.drawImage(img, -this.x, 0, width, height);
 }
 ctx.globalCompositeOperation = "xor";
 },
 random(min, max) {
 return parseInt(Math.floor(Math.random() * (max - min)) + min);
 },
 moveBall(e) {//当点击小红球的时候
 var oldx = e.pageX;
 document.onmousemove = (e) => {//这里要绑定document对象不然你离开的他就不动了
 var x = e.pageX;
 if(this.sliderLeft+x-oldx<=0){//这里判断左边界
 this.sliderLeft = 0;
 }else if(this.sliderLeft+x-oldx>=this.width-this.r*2-this.w){//这里判断右边界
 this.sliderLeft = this.width-this.r*2-this.w;
 }else{
 this.sliderLeft += x - oldx;
 }
 oldx = x;
 };
 this.laveBall();
 },
 laveBall() {//鼠标松开的时候清空状态
 document.onmouseup = ()=> {
 document.onmousemove = null;
 if(this.sliderLeft<(this.x+this.rangeValue)&&this.sliderLeft>(this.x-this.rangeValue)){
 console.log("恭喜你成功了")
 }else{//当没用选中的时候重置一下滑块的位置
 this.sliderLeft = 0;
 }
 };
 },
 },
};
</script>
<style lang="scss" scoped>
.moveSLider {
 position: relative;
 margin: 0 auto;
 height: 50px;
 .react {
 .yuan {
 position: absolute;
 left: 0;
 top: 50%;
 transform: translate(0, -50%);
 width: 30px;
 height: 30px;
 background-color: red;
 border-radius: 50%;
 cursor: pointer;
 }
 position: absolute;
 left: 0;
 top: 50%;
 transform: translate(0, -50%);
 width: 100%;
 height: 20px;
 background-color: rosybrown;
 }
}
.imgDev {
 position: relative;
 margin: 0 auto;
 .slider {
 position: absolute;
 left: 0;
 top: 0;
 background-color: transparent;
 }
}
</style>

drawBlock(ctx, width, height, type, img) {//这里是二合一函数，可以画出阴影部分也切割出拼图形状的函数
 let { w, r, sliderLeft } = this;//w宽度,r圆的半径sliderLeft是滑块的初始位置
 //这地方用随机数每次显示的位置都不同
 var x = this.random(30, width - w - r - 1); //这里最大值为了不让滑块进入隐藏所以要减去滑块的宽度 有个半圆所以要减去半圆位置
 var y = this.random(10, height - w - r - 1);
 if (type == "clip") {//这里要保证在两个东西要在同一个y值上
 x = sliderLeft;
 y = this.y;
 } else {
 this.x = x;
 this.y = y;
 }
 let PI = Math.PI;
 //绘制
 ctx.beginPath();
 //left
 ctx.moveTo(x, y);
 //top
 ctx.arc(x + (w + 5) / 2, y, r, -PI, 0, true);
 ctx.lineTo(x + w + 5, y);
 //right
 ctx.arc(x + w + 5, y + w / 2, r, 1.5 * PI, 0.5 * PI, false);
 ctx.lineTo(x + w + 5, y + w);
 //bottom
 ctx.arc(x + (w + 5) / 2, y + w, r, 0, PI, false);
 ctx.lineTo(x, y + w);
 ctx.arc(x, y + w / 2, r, 0.5 * PI, 1.5 * PI, true);
 ctx.lineTo(x, y);
 if (type == "clip") {
 ctx.shadowBlur = 10;
 ctx.shadowColor = "black";
 }
 ctx.lineWidth = 1;
 ctx.fillStyle = "rgba(0, 0, 0, 0.4)"; //设置背景颜色
 ctx.stroke();
 ctx[type]();
 if (img) {//这里为什么要在这里加载图片呢，因为这个高度是动态的必须计算完之后在放进去
 //还有个原因是你要先剪裁在加载图片
 ctx.drawImage(img, -this.x, 0, width, height);
 }
},