vue项目中实现图片裁剪功能，预览地址.zip

# picture-crop-demo > 在vue项目中实现图片裁剪功能 ## 演示地址 [https://my729.github.io/picture-crop-demo/dist/index.html](https://my729.github.io/picture-crop-demo/dist/index.html) ## 前言 * vue版本：2.6.10 [https://cli.vuejs.org/zh/](https://cli.vuejs.org/zh/) * cropperjs: 1.5.1 [https://github.com/fengyuanchen/cropperjs](https://github.com/fengyuanchen/cropperjs) * elementUI [https://element.eleme.io/#/zh-CN](https://element.eleme.io/#/zh-CN) > 使用 cropperjs插件 和 原生canvas 两种方式实现图片裁剪功能 ## 使用cropperjs插件 ### 安装cropperjs ``` bash yarn install cropperjs ``` ## 初始化一个canvas元素，并在上面绘制图片 ```html <canvas :id="data.src" ref="canvas"></canvas> ``` ``` js // 在canvas上绘制图片 drawImg () { this.$nextTick(() => { // 获取canvas节点 let canvas = document.getElementById(this.data.src) if (canvas) { // 设置canvas的宽为canvas的父元素宽度，宽高比3:2 let parentEle = canvas.parentElement canvas.width = parentEle.offsetWidth canvas.height = 2 * parentEle.offsetWidth / 3 let ctx = canvas.getContext('2d') ctx.clearRect(0, 0, canvas.width, canvas.height) let img = new Image() img.crossOrigin = 'Anonymous' img.src = this.data.src img.onload = function () { ctx.drawImage(img, 0, 0, canvas.width, canvas.height) } } }) } ``` > 如果遇到canvas跨域绘制图片报错，设置图片img.crossOrigin = 'Anonymous'，并且服务器响应头设置Access-Control-Allow-Origin：* ### 创建cropperjs ```js // 引入 import Cropper from 'cropperjs' // 显示裁剪框 initCropper () { let cropper = new Cropper(this.$refs.canvas, { checkCrossOrigin: true, viewMode: 2, aspectRatio: 3 / 2 }) } ``` > 更多方法和属性，参考官网： [https://github.com/fengyuanchen/cropperjs](https://github.com/fengyuanchen/cropperjs) 具体实现，可以查看源码的`cropper.vue` 或 `cropper.one.vue`组件: `cropper.vue组件：`https://github.com/MY729/picture-crop-demo/blob/master/src/components/cropper.vue `cropper.one.vue组件：`https://github.com/MY729/picture-crop-demo/blob/master/src/components/cropper.one.vue `cropper.two.vue组件：`https://github.com/MY729/picture-crop-demo/blob/master/src/components/cropper.two.vue ## 使用canvas实现图片裁剪 > 支持鼠标绘制裁剪框，并移动裁剪框 #### 思路： * 在canvas上绘制图片为背景 * 监听鼠标点击、移动、松开事件 > canvas的isPointInPath()方法： > 如果给定的点的坐标位于路径之内的话（包括路径的边）,否则返回 false 具体实现可查看源码`cropper.canvas.vue组件`: https://github.com/MY729/picture-crop-demo/blob/master/src/components/cropper.canvas.vue ```js cropImg () { let canvas = document.getElementById(this.data.img_url) let ctx = canvas.getContext('2d') let img = new Image() img.onload = function () { ctx.drawImage(img, 0, 0, canvas.width, canvas.height) } img.src = this.data.src let drag = false // 是否拖动矩形 let flag = false // 是否绘制矩形 let rectWidth = 0 // 绘制矩形的宽 let rectHeight = 0 // 绘制矩形的高 let clickX = 0 // 矩形开始绘制X坐标 let clickY = 0 // 矩形开始绘制Y坐标 let dragX = 0 // 当要拖动矩形点击时X坐标 let dragY = 0 // 当要拖动矩形点击时Y坐标 let newRectX = 0 // 拖动变化后矩形开始绘制的X坐标 let newRectY = 0 // 拖动变化后矩形开始绘制的Y坐标 // 鼠标按下 canvas.onmousedown = e => { // 每次点击前如果有绘制好的矩形框，通过路径绘制出来，用于下面的判断 ctx.beginPath() ctx.setLineDash([6, 6]) ctx.moveTo(newRectX, newRectY) ctx.lineTo(newRectX + rectWidth, newRectY) ctx.lineTo(newRectX + rectWidth, newRectY + rectHeight) ctx.lineTo(newRectX, newRectY + rectHeight) ctx.lineTo(newRectX, newRectY) ctx.strokeStyle = 'green' ctx.stroke() // 每次点击，通过判断鼠标点击的点在矩形框内还是外，来决定重新绘制还是移动矩形框 if (ctx.isPointInPath(e.offsetX, e.offsetY)) { drag = true dragX = e.offsetX dragY = e.offsetY clickX = newRectX clickY = newRectY } else { ctx.clearRect(0, 0, canvas.width, canvas.height) ctx.drawImage(img, 0, 0, canvas.width, canvas.height) flag = true clickX = e.offsetX clickY = e.offsetY newRectX = e.offsetX newRectY = e.offsetY } } // 鼠标抬起 canvas.onmouseup = () => { if (flag) { flag = false this.sureCrop(clickX, clickY, rectWidth, rectHeight) } if (drag) { drag = false this.sureCrop(newRectX, newRectY, rectWidth, rectHeight) } } // 鼠标移动 canvas.onmousemove = (e) => { if (flag) { ctx.clearRect(0, 0, canvas.width, canvas.height) ctx.drawImage(img, 0, 0, canvas.width, canvas.height) rectWidth = e.offsetX - clickX rectHeight = e.offsetY - clickY ctx.beginPath() ctx.strokeStyle = '#FF0000' ctx.strokeRect(clickX, clickY, rectWidth, rectHeight) ctx.closePath() } if (drag) { ctx.clearRect(0, 0, canvas.width, canvas.height) ctx.drawImage(img, 0, 0, canvas.width, canvas.height) ctx.beginPath() newRectX = clickX + e.offsetX - dragX newRectY = clickY + e.offsetY - dragY ctx.strokeStyle = 'yellow' ctx.strokeRect(newRectX, newRectY, rectWidth, rectHeight) ctx.closePath() } } }, // 拿到裁剪后的参数，可自行处理图片 sureCrop (x, y, width, height) { let canvas = document.getElementById(this.data.img_url + 'after') // 设置canvas的宽为canvas的父元素宽度，宽高比3:2 let parentEle = canvas.parentElement canvas.width = parentEle.offsetWidth canvas.height = 2 * parentEle.offsetWidth / 3 let ctx = canvas.getContext('2d') let img = new Image() img.src = this.data.src img.onload = function () { ctx.beginPath() ctx.moveTo(x, y) ctx.lineTo(x + width, y) ctx.lineTo(x + width, y + height) ctx.lineTo(x, y + height) ctx.clip() ctx.drawImage(img, 0, 0, canvas.width, canvas.height) } ctx.stroke() } ``` #### 可以直接clone项目，本地运行查看代码和效果 ## Project setup ``` yarn install ``` ### Compiles and hot-reloads for development ``` yarn run serve ``` ### Compiles and minifies for production ``` yarn run build ``` ### Lints and fixes files ``` yarn run lint ``` ### Customize configuration See [Configuration Reference](https://cli.vuejs.org/config/).