使用canvas怎么实现一个图片打码功能？很多新手对此不是很清楚，为了帮助大家解决这个难题，下面小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。
首先创建一个html文件, 并引入 vue 和 elelment-ui(注意还有样式文件)
<!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> <!-- elelment-ui样式 --> <link rel="stylesheet" href="https://unpkg.com/element-ui/lib/theme-chalk/index.css"></head><body> </body><!-- 引入vue --><script src="https://cdn.jsdelivr.net/npm/vue"></script><!-- 引入element-ui --><script src="https://unpkg.com/element-ui/lib/index.js"></script></html>接下来就可以写我们的打码功能啦
实现思路
创建canvas画布，并将要打码的图片绘制上去
监听鼠标在图片上的点击，移动、松开事件，在canvas画布上绘制要打码的区域
处理绘制的打码区域
保存打码后的图片
将要打码的图片绘制到canvas画布上
// 初始化 绘制图片toCode (currentImg) { this.$nextTick(() => { // 获取将要绘制的canvas的父元素节点 let parentId = document.getElementById('parentId') // 初始化图片 let drawImg = new Image() drawImg.setAttribute('crossOrigin', 'anonymous') drawImg.crossOrigin = 'Anonymous' drawImg.src = currentImg // 创建canvas元素并添加到父节点中 let addCanvas = document.createElement('canvas') parentId.appendChild(addCanvas) let canvas = parentId.lastElementChild canvas.id = 'imgCanvas' if (canvas.getContext) { let ctx = canvas.getContext('2d') // 绘制图片 drawImg.onload = function () { canvas.width = 720 canvas.height = 500 ctx.drawImage(drawImg, 0, 0, 720, 500) } } })}点击打码按钮，绘制打码区域
思路：
鼠标点击，获取点击时的坐标，每次点击前可能会存在打过码的区域，先清除画布，重新绘制图片
鼠标移动，开始绘制打码的矩形，通过移动的坐标和上面点击的点坐标确定绘制的矩形坐标和宽高
将绘制的打码矩形，分割成一个个宽高15像素的小正方形，并给每个小正方形生产随机颜色
鼠标松开，停止绘制矩形
// 打码dialogCode (img) { let parentId = document.getElementById('parentId') let canvas = document.getElementById('imgCanvas') if (canvas.getContext) { let ctx = canvas.getContext('2d') let drawImage = new Image() drawImage.crossOrigin = 'Anonymous' drawImage.src = img drawImage.onload = () => { ctx.drawImage(drawImage, 0, 0, 720, 500) } // 鼠标点击 parentId.onmousedown = e => { ctx.clearRect(0, 0, canvas.width, canvas.height) ctx.drawImage(drawImage, 0, 0, 720, 500) this.flag = true this.clickX = e.offsetX // 鼠标点击时的X this.clickY = e.offsetY // 鼠标点击时的Y } // 鼠标松开 parentId.onmouseup = () => { this.flag = false } // 鼠标按下 parentId.onmousemove = e => { if (this.flag) { ctx.clearRect(0, 0, canvas.width, canvas.height) ctx.drawImage(drawImage, 0, 0, 720, 500) ctx.beginPath() let pixels = [] // 二维数组，每个子数组有5个值（绘制矩形左上角的X坐标、y坐标，矩形的宽、高，生成的4位随机数用于颜色值） for (let x = 0; x < (e.offsetX - this.clickX) / 15; x++) { for (let y = 0; y < (e.offsetY - this.clickY) / 15; y++) { pixels.push([(x * 15 + this.clickX), (y * 15 + this.clickY), 15, 15, Math.floor(Math.random() * 9999)]) } for (let y = 0; y > (e.offsetY - this.clickY) / 15; y--) { pixels.push([(x * 15 + this.clickX), (y * 15 + this.clickY), 15, 15, Math.floor(Math.random() * 9999)]) } } for (let x = 0; x > (e.offsetX - this.clickX) / 15; x--) { for (let y = 0; y > (e.offsetY - this.clickY) / 15; y--) { pixels.push([(x * 15 + this.clickX), (y * 15 + this.clickY), 15, 15, Math.floor(Math.random() * 9999)]) } for (let y = 0; y < (e.offsetY - this.clickY) / 15; y++) { pixels.push([(x * 15 + this.clickX), (y * 15 + this.clickY), 15, 15, Math.floor(Math.random() * 9999)]) } } // 遍历数组绘制小正方形块 for (let i = 0; i < pixels.length; i++) { ctx.fillStyle = '#bf' + pixels[i][4] ctx.fillRect(pixels[i][0], pixels[i][1], pixels[i][2], pixels[i][3]) } ctx.fill() ctx.closePath() } } }}保存
// 保存dialogUpload () { let canvas = document.getElementById('imgCanvas') let tempImg = canvas.toDataURL('image/png') let imgURL = document.getElementById('imgURL') imgURL.crossOrigin = 'Anonymous' imgURL.src = tempImg}源码
复制到html文件可预览
<!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>使用canvas一步步实现图片打码功能</title> <!-- elelment-ui样式 --> <link rel="stylesheet" href="https://unpkg.com/element-ui/lib/theme-chalk/index.css"> <style type="text/css"> .rc-code__buttons { margin: 20px; } </style></head><body> <div id="app"> <div class="rc-code__buttons"> <h2>vue项目中使用canvas一步步实现图片打码功能</h2> <el-button type="primary" @click="dialogCode(data.img_url)">打码</el-button> <el-button type="success" @click="dialogUpload()">保存</el-button> </div> <el-row> <el-col :span="12"><h4>点击打码按钮，在图片上绘制打码区域； 点击保存，生成打码后的图片</h4></el-col> <el-col :span="12"><h4>保存后的图片</h4></el-col> <el-col :span="12"><div id="parentId"></div></el-col> <el-col :span="12"><img id="imgURL"/></el-col> </el-row> </div></body><!-- 引入vue --><script src="https://cdn.jsdelivr.net/npm/vue"></script><!-- 引入element-ui --><script src="https://unpkg.com/element-ui/lib/index.js"></script><script>new Vue({ el: '#app', data () { return { data: { img_url: 'https://avatars0.githubusercontent.com/u/26196557?s=460&v=4' }, flag: false, // 是否绘制矩形 clickX: '', // 开始绘制矩形时，鼠标点击时的x坐标 clickY: '' // 开始绘制矩形时，鼠标点击时的y坐标 } }, mounted() { this.toCode(this.data.img_url) }, methods: { // 初始化 绘制图片 toCode (currentImg) { this.$nextTick(() => { let parentId = document.getElementById('parentId') let drawImg = new Image() drawImg.setAttribute('crossOrigin', 'anonymous') drawImg.crossOrigin = 'Anonymous' drawImg.src = currentImg let addCanvas = document.createElement('canvas') parentId.appendChild(addCanvas) let canvas = parentId.lastElementChild canvas.id = 'imgCanvas' if (canvas.getContext) { let ctx = canvas.getContext('2d') drawImg.onload = function () { canvas.width = 720 canvas.height = 500 ctx.drawImage(drawImg, 0, 0, 720, 500) } } }) }, // 打码 dialogCode (img) { let parentId = document.getElementById('parentId') let canvas = document.getElementById('imgCanvas') if (canvas.getContext) { let ctx = canvas.getContext('2d') let drawImage = new Image() drawImage.crossOrigin = 'Anonymous' drawImage.src = img drawImage.onload = () => { ctx.drawImage(drawImage, 0, 0, 720, 500) } parentId.onmousedown = e => { ctx.clearRect(0, 0, canvas.width, canvas.height) ctx.drawImage(drawImage, 0, 0, 720, 500) this.flag = true this.clickX = e.offsetX // 鼠标点击时的X this.clickY = e.offsetY // 鼠标点击时的Y } parentId.onmouseup = () => { this.flag = false } parentId.onmousemove = e => { if (this.flag) { ctx.clearRect(0, 0, canvas.width, canvas.height) ctx.drawImage(drawImage, 0, 0, 720, 500) ctx.beginPath() let pixels = [] // 二维数组，每个子数组有5个值（绘制矩形左上角的X坐标、y坐标，矩形的宽、高，生成的4位随机数用于颜色值） for (let x = 0; x < (e.offsetX - this.clickX) / 15; x++) { for (let y = 0; y < (e.offsetY - this.clickY) / 15; y++) { pixels.push([(x * 15 + this.clickX), (y * 15 + this.clickY), 15, 15, Math.floor(Math.random() * 9999)]) } for (let y = 0; y > (e.offsetY - this.clickY) / 15; y--) { pixels.push([(x * 15 + this.clickX), (y * 15 + this.clickY), 15, 15, Math.floor(Math.random() * 9999)]) } } for (let x = 0; x > (e.offsetX - this.clickX) / 15; x--) { for (let y = 0; y > (e.offsetY - this.clickY) / 15; y--) { pixels.push([(x * 15 + this.clickX), (y * 15 + this.clickY), 15, 15, Math.floor(Math.random() * 9999)]) } for (let y = 0; y < (e.offsetY - this.clickY) / 15; y++) { pixels.push([(x * 15 + this.clickX), (y * 15 + this.clickY), 15, 15, Math.floor(Math.random() * 9999)]) } } for (let i = 0; i < pixels.length; i++) { ctx.fillStyle = '#bf' + pixels[i][4] ctx.fillRect(pixels[i][0], pixels[i][1], pixels[i][2], pixels[i][3]) } ctx.fill() ctx.closePath() } } } }, // 保存 dialogUpload () { let canvas = document.getElementById('imgCanvas') let tempImg = canvas.toDataURL('image/png') let imgURL = document.getElementById('imgURL') imgURL.crossOrigin = 'Anonymous' imgURL.src = tempImg } }})</script></html>看完上述内容是否对您有帮助呢？如果还想对相关知识有进一步的了解或阅读更多相关文章，请关注编程网行业资讯频道，感谢您对编程网的支持。
