其实绘制图形二维码就是使用 进行图形绘制

canvas 绘制图形

1.获取元素dom 访问绘图上下文

<canvas id="tutorial" width="150" height="150"></canvas>
var canvas = document.getElementById('tutorial'); //获取dom
var ctx = canvas.getContext('2d'); //访问绘图上下文

2.第二步就是绘制相应内容了，下面是vue 绘制验证码图形

如图：[在这里插入图片描述](https://img-blog.csdnimg.cn/2019071512072254.png

1.父组件login.vue

<template>
    <div class="login-wrap">
        <div class="ms-login">
            <div class="ms-title">后台管理系统</div>
            <el-form :model="ruleForm" :rules="rules" ref="ruleForm" label-width="0px" class="ms-content">
                <el-form-item prop="username">
                    <el-input v-model="ruleForm.username" placeholder="username">
                        <el-button slot="prepend" icon="el-icon-people"></el-button>
                    </el-input>
                </el-form-item>
                <el-form-item prop="password">
                    <el-input type="password" placeholder="password" v-model="ruleForm.password" @keyup.enter.native="submitForm('ruleForm')">
                        <el-button slot="prepend" icon="el-icon-lock"></el-button>
                    </el-input>
                </el-form-item>

                <el-form-item prop="sidentify"> // 验证码
                    <el-col :span="14">
                    <el-input placeholder="sidentify" v-model="ruleForm.password" @keyup.enter.native="submitForm('ruleForm')">
                    </el-input>
                    </el-col>
                    <el-col :span="8">
                        <v-sidentify></v-sidentify>
                    </el-col>
                </el-form-item>
                <div class="login-btn">
                    <el-button type="primary" @click="submitForm('ruleForm')">登录</el-button>
                </div>
                <p class="login-tips">Tips : 用户名和密码随便填。</p>
            </el-form>
        </div>
    </div>
</template>

<script>
    import Sidentify from '../components/common/Sidentify'  //**引入验证码组件**
    export default {
        data: function(){
            return {
                ruleForm: {
                    username: '',
                    password: '',
                    sidentify: '',
                },
                rules: {
                    username: [
                        { required: true, message: '请输入用户名', trigger: 'blur' }
                    ],
                    password: [
                        { required: true, message: '请输入密码', trigger: 'blur' }
                    ],
                    sidentify:[
                        {required: true}
                    ]
                }
            }
        },
        components: {
            'v-sidentify':Sidentify 
        },
      
    }
</script>

2. 创建验证码组件

<template>
    <div class="s-canvas">
        <canvas id="s-canvas" :width="contentWidth" :height="contentHeight"></canvas>
    </div>
</template>
<script>
    export default {
        name: 'SIdentify',
        props: {
            identifyCode: {
                type: String,
                default: 'asdf'
            },

        },
        data(){
            return {
                fontSizeMin: 160,
                fontSizeMax: 40,
                backgroundColorMin: 180,
                backgroundColorMax:240,
                colorMin: 50,
                colorMax: 160,
                lineColorMin:40,
                lineColorMax: 180,
                dotColorMin: 0,
                dotColorMax: 255,
                contentWidth: 112,
                contentHeight: 38
            }
        },
        methods: {
            // 生成一个随机数
            randomNum(min, max) {
                return Math.floor(Math.random() * (max - min) + min)
            },
            // 生成一个随机的颜色
            randomColor(min, max) {
                let r = this.randomNum(min, max)
                let g = this.randomNum(min, max)
                let b = this.randomNum(min, max)
                return 'rgb(' + r + ',' + g + ',' + b + ')'
            },
            drawPic() {
                let canvas = document.getElementById('s-canvas')
                let ctx = canvas.getContext('2d')
                // ctx.textBaseline = 'bottom'
                // 绘制背景
                ctx.fillStyle = this.randomColor(this.backgroundColorMin, this.backgroundColorMax) //图形填充颜色设置
                ctx.strokeStyle = this.randomColor(this.backgroundColorMin, this.backgroundColorMax) //图形轮廓的颜色设置
                ctx.fillRect(0, 0, this.contentWidth, this.contentHeight) //绘制一个填充的矩形 0 0 width height x起点 y起点  宽 高
                ctx.strokeRect(0,0,this.contentWidth, this.contentHeight) // 绘制一个矩形边框 0 0 width height x起点 y起点  宽 高
                // ctx.clearRect(50,0,this.contentWidth,this.contentHeight)  //清除指定矩形区域，清除部分完全透明
                // 绘制文字
                for (let i = 0; i < this.identifyCode.length; i++) {
                    this.drawText(ctx, this.identifyCode[i], i)
                }
                this.drawLine(ctx)
                this.drawDot(ctx)
            },
            drawText(ctx, txt, i) {
                ctx.fillStyle = this.randomColor(this.colorMin, this.colorMax)
                ctx.font = this.randomNum(this.fontSizeMin, this.fontSizeMax) + 'px SimHei' //字体大小
                ctx.textBaseline = 'alphabetic' //基线对齐
                let x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1))
                let y = this.randomNum(this.fontSizeMax, this.contentHeight - 5)
                var deg = this.randomNum(-45, 45)
                // 修改坐标原点和旋转角度
                ctx.translate(x, y)//移动不同位置  参数偏移量
                ctx.rotate(deg * Math.PI / 180) //旋转 参数角度
                ctx.fillText(txt, 0, 0)
                // 恢复坐标原点和旋转角度
                ctx.rotate(-deg * Math.PI / 180)
                ctx.translate(-x, -y)
            },
            drawLine(ctx) {
                // 绘制干扰线
                for (let i = 0; i < 8; i++) {
                    ctx.strokeStyle = this.randomColor(this.lineColorMin, this.lineColorMax)
                    ctx.beginPath() //新建一条路径
                    ctx.moveTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight)) //设置起点x,y
                    ctx.lineTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight)) //绘制直线 x,y 一条当前位置到x,y点的直线
                    ctx.stroke() // 通过线条绘制图形轮廓
                    // ctx.closePath() //结束闭合路径
                }
            },
            drawDot(ctx) {
                // 绘制干扰点
                for (let i = 0; i < 100; i++) {
                    ctx.fillStyle = this.randomColor(0, 255)
                    ctx.beginPath()
                    // 绘制圆弧或圆，x,y,radius，startAngle,endAngle,anticlockwise // x,y 圆心点，radius 半径，从startAngle开始到endAngle结束
                    ctx.arc(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight), 1, 0, 2 * Math.PI)
                    ctx.fill() //通过填充路径的内容区域生成实心的图形。
                }
            }
        },
        watch: {
            identifyCode() {
                this.drawPic()
            }
        },
        mounted() {
            this.drawPic()
        }
    }
</script>