缘由：之前看哔哩哔哩官网登录的时候有一个拼图验证码，很好奇怎么去实现。然后就想着自己弄一个。先给大家看我的最终效果。后面再一点点拆解代码。

为什么想着写这个功能呢，主要在于拼图验证码在前端这里会比较复杂并且深入。相比文字拼写，12306的图片验证码都没有拼图验证码对前端的要求来的复杂，和难。

我总结下知识点：

1、弹窗功能

2、弹窗基于元素定位

3、元素拖动

4、canvas绘图

5、基础逻辑

一、弹窗和弹窗组件

抱歉，这里我偷懒了直接用了elementUI的el-popover组件，所以小伙伴不懂的直接看elementUI官网的说明。

我个人也研究和编写了这块的组件功能（基于popper.js）

二、编写基础结构

这块属于html的基础内容，也就标题党了

三、canvas绘制图片

1、canvas绘制外部img图片

代码：

let mainDom = document.querySelector("#codeImg");let bg = mainDom.getContext("2d");let width = mainDom.width;let height = mainDom.height;let blockDom = document.querySelector("#sliderBlock");let block = blockDom.getContext("2d");//重新赋值，让canvas进行重新绘制blockDom.height = height;mainDom.height = height;let imgsrc = require("../assets/images/back.jpg");let img = document.createElement("img");img.style.objectFit = "scale-down";img.src = imgsrc;img.onload = function() { bg.drawImage(img, 0, 0, width, height); block.drawImage(img, 0, 0, width, height);};复制代码

这里我绘制了两个canvas，因为一个是背景一个是滑块

核心在于

let mainDom = document.querySelector("#codeImg");let imgsrc = require("../assets/images/back.jpg");let bg = mainDom.getContext("2d");let img = document.createElement("img");img.onload = function() { bg.drawImage(img, 0, 0, width, height);};复制代码

2、canvas绘制滑块部分

就是这个图，这个有一些知识点，不难，但是很复杂。

具体请看：

代码部分：

drawBlock(ctx, xy = { x: 254, y: 109, r: 9 }, type) { let x = xy.x, y = xy.y, r = xy.r, w = 40; 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); //修饰，没有会看不出效果 ctx.lineWidth = 1; ctx.fillStyle = "rgba(255, 255, 255, 0.5)"; ctx.strokeStyle = "rgba(255, 255, 255, 0.5)"; ctx.stroke(); ctx[type](); ctx.globalCompositeOperation = "xor";}复制代码

解释下：

参数是传入canvas对象

x，y轴数据

剪切还是填充的canvas函数（fill，clip）

绘制难点：（很重要，不然你没法理解它怎么绘制的）

绘制主要是需要理解这里的绘制是根据你设置一个起始点坐标，然后你绘制第二次的时候线就会连接到第二个点，依次连接最后回到原点就形成一个完整的图形。

圆形的绘制：来自：

用的是arc参数，主要是看这个图

fill是用于填充绘制的部分，clip是裁剪出绘制的部分，利用这个就可以出现一个扣掉的图片和一个裁剪出来的图片。

完成之后就是我的那个函数了。大家可以直接拿去用。

3、让元素跟随鼠标点击之后滑动

这里其实原理非常简单，就是有一个注意点。

原理：

鼠标点击之后记录当前坐标，然后随着（mousemove）滚动的时候修改元素的left和top值就行了。

还有一点就是鼠标快速滑动会导致丢失滑动效果，这里需要用document，不能是元素级别的监听。

元素上面我只需要鉴定按下mousedown

代码：

//鼠标按下drag(e) { console.log("鼠标按下", e); let dom = e.target; //dom元素 let slider = document.querySelector("#sliderBlock"); //滑块dom const downCoordinate = { x: e.x, y: e.y }; //正确的滑块数据 let checkx = Number(this.slider.mx) - Number(this.slider.bx); //x轴数据 let x = 0; const move = moveEV => { x = moveEV.x - downCoordinate.x; //y = moveEV.y - downCoordinate.y; if (x >= 251 || x <= 0) return false; dom.style.left = x + "px"; //dom.style.top = y + "px"; slider.style.left = x + "px"; }; const up = () => { document.removeEventListener("mousemove", move); document.removeEventListener("mouseup", up); dom.style.left = ""; console.log(x, checkx); let max = checkx - 5; let min = checkx - 10; //允许正负误差1 if ((max >= x && x >= min) || x === checkx) { console.log("滑动解锁成功"); this.puzzle = true; this.tips = "验证成功"; setTimeout(() => { this.visible = false; }, 500); } else { console.log("拼图位置不正确"); this.tips = "验证失败，请重试"; this.puzzle = false; this.canvasInit(); } }; document.addEventListener("mousemove", move); document.addEventListener("mouseup", up);}复制代码

4、总结

核心点比较多，写过之后发现不难，关键在于去写

个人该页面git地址：

该页面处于项目的

路由访问为：

5、完整的页面代码

<template> <div id="login"> <el-form class="loginFrom" :model="logindata" :rules="rules" ref="ruleForm"> <el-form-item class="login-item"> <h1 class="login-title">海天酱油登录中心</h1> </el-form-item> <el-form-item prop="userName"> <el-input class="login-inputorbuttom" prefix-icon="el-icon-user" placeholder="登录名" v-model="logindata.userName" ></el-input> </el-form-item> <el-form-item prop="password"> <el-input class="login-inputorbuttom" prefix-icon="el-icon-lock" placeholder="密码" v-model="logindata.password" ></el-input> </el-form-item> <!--<el-form-item prop="verificationCode"> <el-input class="login-inputorbuttom" v-model="logindata.verificationCode" ></el-input> </el-form-item>--> <el-form-item class="login-item"> <el-button class="login-inputorbuttom login-bottom" type="primary" v-popover:popover @click="visible = !visible" >登 录</el-button > </el-form-item> </el-form> <!--验证码弹窗--> <el-popover popper-class="slidingPictures" ref="popover" trigger="manual" v-model="visible" > <div class="sliding-pictures"> <div class="vimg"> <canvas id="sliderBlock"></canvas> <canvas id="codeImg"></canvas> </div> <div class="slider"> <div class="track" :class="{ pintuTrue: puzzle }"> {{ tips }} </div> <div class="button el-icon-s-grid" @mousedown.prevent="drag"></div> </div> <div class="operation"> <span title="关闭验证码" @click="visible = false" class="el-icon-circle-close" ></span> <span title="刷新验证码" @click="canvasInit" class="el-icon-refresh-left" ></span> </div> </div> </el-popover> </div></template><script>export default { name: "login", data() { return { tips: "拖动左边滑块完成上方拼图", logindata: { userName: "", password: "", verificationCode: "" }, rules: {}, visible: false, //滑块x轴数据 slider: { mx: 0, bx: 0 }, //拼图是否正确 puzzle: false }; }, watch: { visible(e) { if (e === true) { this.canvasInit(); this.puzzle = false; } } }, beforeCreate() {}, created() {}, beforeMount() {}, mounted() {}, methods: { //拼图验证码初始化 canvasInit() { //生成指定区间的随机数 const random = (min, max) => { return Math.floor(Math.random() * (max - min + 1) + min); }; //x: 254, y: 109 let mx = random(127, 244), bx = random(10, 128), y = random(10, 99); this.slider = { mx, bx }; this.draw(mx, bx, y); }, //鼠标按下 drag(e) { console.log("鼠标按下", e); let dom = e.target; //dom元素 let slider = document.querySelector("#sliderBlock"); //滑块dom const downCoordinate = { x: e.x, y: e.y }; //正确的滑块数据 let checkx = Number(this.slider.mx) - Number(this.slider.bx); //x轴数据 let x = 0; const move = moveEV => { x = moveEV.x - downCoordinate.x; //y = moveEV.y - downCoordinate.y; if (x >= 251 || x <= 0) return false; dom.style.left = x + "px"; //dom.style.top = y + "px"; slider.style.left = x + "px"; }; const up = () => { document.removeEventListener("mousemove", move); document.removeEventListener("mouseup", up); dom.style.left = ""; console.log(x, checkx); let max = checkx - 5; let min = checkx - 10; //允许正负误差1 if ((max >= x && x >= min) || x === checkx) { console.log("滑动解锁成功"); this.puzzle = true; this.tips = "验证成功"; setTimeout(() => { this.visible = false; }, 500); } else { console.log("拼图位置不正确"); this.tips = "验证失败，请重试"; this.puzzle = false; this.canvasInit(); } }; document.addEventListener("mousemove", move); document.addEventListener("mouseup", up); }, draw(mx = 200, bx = 20, y = 50) { let mainDom = document.querySelector("#codeImg"); let bg = mainDom.getContext("2d"); let width = mainDom.width; let height = mainDom.height; let blockDom = document.querySelector("#sliderBlock"); let block = blockDom.getContext("2d"); //重新赋值，让canvas进行重新绘制 blockDom.height = height; mainDom.height = height; let imgsrc = require("../assets/images/back.jpg"); let img = document.createElement("img"); img.style.objectFit = "scale-down"; img.src = imgsrc; img.onload = function() { bg.drawImage(img, 0, 0, width, height); block.drawImage(img, 0, 0, width, height); }; let mainxy = { x: mx, y: y, r: 9 }; let blockxy = { x: bx, y: y, r: 9 }; this.drawBlock(bg, mainxy, "fill"); this.drawBlock(block, blockxy, "clip"); }, //绘制拼图 drawBlock(ctx, xy = { x: 254, y: 109, r: 9 }, type) { let x = xy.x, y = xy.y, r = xy.r, w = 40; 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); //修饰，没有会看不出效果 ctx.lineWidth = 1; ctx.fillStyle = "rgba(255, 255, 255, 0.5)"; ctx.strokeStyle = "rgba(255, 255, 255, 0.5)"; ctx.stroke(); ctx[type](); ctx.globalCompositeOperation = "xor"; } }};</script><style>.slidingPictures { padding: 0; width: 300px; border-radius: 2px;}</style><style scoped lang="scss">#login { display: flex; flex-flow: row; justify-content: flex-end; align-items: center; width: 100%; height: 100%; background-image: url("../assets/images/back.jpg"); background-size: 100% 100%; .loginFrom { width: 300px; margin-top: -10vw; margin-right: 10vw; .login-item { display: flex; justify-content: center; align-items: center; } .login-title { color: #ffffff; font-size: 16px; margin-bottom: 10px; } .login-bottom { margin-top: 15px; } .login-bottom:hover { background: rgba(28, 136, 188, 0.5); } .login-bottom:active { background: rgba(228, 199, 200, 0.5); } /deep/.login-inputorbuttom { height: 40px; width: 300px; background: rgba(57, 108, 158, 0.5); border-radius: 20px; border: #396c9e 1px solid; font-size: 14px; color: #ffffff; .el-input--small, .el-input__inner { line-height: 43px; border: none; color: #ffffff; font-size: 14px; height: 40px; border-radius: 20px; background: transparent; text-align: center; } .el-input__icon { line-height: 40px; font-size: 16px; } } }}/*该样式最终是以弹窗插入*/.sliding-pictures { width: 100%; .vimg { width: 100%; height: 170px; #codeImg, #sliderBlock { padding: 7px 7px 0 7px; width: inherit; height: inherit; } #codeImg { //display: none; } #sliderBlock { position: absolute; z-index: 4000; } } .slider { width: 100%; height: 65px; border-bottom: #c7c9d0 1px solid; display: flex; align-items: center; justify-content: flex-start; .track { margin-left: 7px; width: 286px; height: 38px; background: rgba(28, 136, 188, 0.5); border-radius: 25px; font-size: 14px; line-height: 38px; padding-right: 15px; padding-left: 70px; } .pintuTrue { background: #67c23a; color: #ffffff; } .button { position: absolute; width: 50px; height: 50px; line-height: 48px; background: #ffffff; box-shadow: #b9bdc8 0 0 3px; border-radius: 50%; left: 7px; text-align: center; font-size: 28px; color: #3e5d8b; &:hover { color: #2181bd; } } } .operation { width: 100%; height: 40px; > span { color: #9fa3ac; display: inline-block; width: 40px; font-size: 25px; line-height: 40px; text-align: center; &:hover { background: #e2e8f5; } } }}</style>