本篇文章主要介绍了vue实现裁切图片同时实现放大、缩小、旋转功能，分享给大家，具体如下：
实现效果：
裁切指定区域内的图片
旋转图片
放大图片
输出bolb 格式数据 提供给 formData 对象
效果图
大概原理：
利用h5 FileReader 对象， 获取 <input type="file"/> “上传到浏览器的文件” ，文件形式 为base64形式， 把 base64 赋给canvas的上下文。
然后给canvas 元素上加入对（mousedown）监听事件。 当用户鼠标左键在canvas按下时：
挂载对 window 对象mousemove事件 ---> 获取 鼠标移动x,y距离.从而操作 canvas里的图像的位置移动。
挂载对 window 对象mouseup 事件， 清除 mousemove事件的绑定。（同时该事件触发后会被删除）
剩下的 放大、缩小 、 旋转 是对 canvas 对象的操作/坐标体系的操作。具体api详见mdn canvas 文档
代码
dom.js
export const on = ({el, type, fn}) => { if (typeof window) { if (window.addEventListener) { el.addEventListener(type, fn, false) } else { el.attachEvent(`on${type}`, fn) } } } export const off = ({el, type, fn}) => { if (typeof window) { if (window.addEventListener) { el.removeEventListener(type, fn) } else { el.detachEvent(`on${type}`, fn) } } } export const once = ({el, type, fn}) => { const hyFn = (event) => { try { fn(event) } finally { off({el, type, fn: hyFn}) } } on({el, type, fn: hyFn}) } // 最后一个 export const fbTwice = ({fn, time = 300}) => { let [cTime, k] = [null, null] // 获取当前时间 const getTime = () => new Date().getTime() // 混合函数 const hyFn = () => { const ags = argments return () => { clearTimeout(k) k = cTime = null fn(...ags) } } return () => { if (cTime == null) { k = setTimeout(hyFn(...arguments), time) cTime = getTime() } else { if ( getTime() - cTime < 0) { // 清除之前的函数堆 ---- 重新记录 clearTimeout(k) k = null cTime = getTime() k = setTimeout(hyFn(...arguments), time) } }} } export const contains = function(parentNode, childNode) { if (parentNode.contains) { return parentNode != childNode && parentNode.contains(childNode) } else { return !!(parentNode.compareDocumentPosition(childNode) & 16) } } export const addClass = function (el, className) { if (typeof el !== "object") { console.log('el is not elem') return null } let classList = el['className'] classList = classList === '' ? [] : classList.split(/\s+/) if (classList.indexOf(className) === -1) { classList.push(className) el.className = classList.join(' ') } else { console.warn('warn className current') } } export const removeClass = function (el, className) { let classList = el['className'] classList = classList === '' ? [] : classList.split(/\s+/) classList = classList.filter(item => { return item !== className }) el.className = classList.join(' ') } export const delay = ({fn, time}) => { let oT = null let k = null return () => { // 当前时间 let cT = new Date().getTime() const fixFn = () => { k = oT = null fn() } if (k === null) { oT = cT k = setTimeout(fixFn, time) return } if (cT - oT < time) { oT = cT clearTimeout(k) k = setTimeout(fixFn, time) } } } export const Event = function () { // 类型 this.typeList = {} } Event.prototype.on = function ({type, fn}){ if (this.typeList.hasOwnProperty(type)) { this.typeList[type].push(fn) } else { this.typeList[type] = [] this.typeList[type].push(fn) } } Event.prototype.off = function({type, fn}) { if (this.typeList.hasOwnProperty(type)) { let list = this.typeList[type] let index = list.indexOf(fn) if (index !== -1 ) { list.splice(index, 1) } } else { console.warn('not has this type') } } Event.prototype.once = function ({type, fn}) { const fixFn = () => { fn() this.off({type, fn: fixFn}) } this.on({type, fn: fixFn}) } Event.prototype.trigger = function (type){ if (this.typeList.hasOwnProperty(type)) { this.typeList[type].forEach(fn => { fn() }) } }
组件模板