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vue 实现 裁切图片 同时有放大、缩小、旋转功能

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08/03
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实现效果：

  1. 裁切指定区域内的图片
  2. 旋转图片
  3. 放大图片
  4. 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：

  1. 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。
  2. 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

<template>
<div class="jc-clip-image" :style="{width: `${clip.width}`}">
<canvas ref="ctx"
:width="clip.width"
:height="clip.height"
@mousedown="handleClip($event)"
>
</canvas>
<input type="file" ref="file" @change="readFileMsg($event)">
<div class="clip-scale-btn">
<a class="add" @click="handleScale(false)">+</a>
<a @click="rotate" class="right-rotate">转</a>
<a class="poor" @click="handleScale(true)">-</a>
<span>{{scale}}</span>
</div>
<div class="upload-warp">
<a class="upload-btn" @click="dispatchUpload($event)">upload</a>
<a class="upload-cancel">cancel</a>
</div>
<div class="create-canvas">
<a class="to-send-file" @click="outFile" title="请打开控制台">生成文件</a>
</div>
</div>
</template>
<script>
import {on, off, once} from '../../utils/dom'
export default {
ctx: null,
file: null,
x: 0, // 点击canvas x 鼠标地址
y: 0,// 点击canvas y 鼠标地址
xV: 0, // 鼠标移动 x距离
yV: 0, // 鼠标移动 y距离
nX: 0, // 原始坐标点 图像 x
nY: 0,// 原始坐标点 图像 y
img: null,
props: {
src: {
type: String,
default: null
},
clip: {
type: Object,
default () {
return {width: '200px', height: '200px'}
}
}
},
data () {
return {
isShow: false,
base64: null,
scale: 1.5, //放大比例
deg: 0 //旋转角度
}
},
computed: {
width () {
const {clip} = this
return parseFloat(clip.width.replace('px', ''))
},
height () {
const {clip} = this
return parseFloat(clip.height.replace('px', ''))
}
},
mounted () {
const {$options, $refs, width, height} = this
// 初始化 canvas file nX nY
Object.assign($options, {
ctx: $refs.ctx.getContext('2d'),
file: $refs.file,
nX: -width / 2,
nY: -height / 2
})
},
methods: {
// 旋转操作
rotate () {
const {$options, draw} = this
this.deg = (this.deg + Math.PI /2)% (Math.PI * 2)
draw($options.img, $options.nX + $options.xV, $options.nY + $options.yV, this.scale, this.deg)
},
// 处理放大
handleScale (flag) {
const {$options, draw, deg} = this
flag && this.scale > 0.1 && (this.scale = this.scale - 0.1)
!flag && this.scale < 1.9 && (this.scale = this.scale + 0.1)
$options.img && draw($options.img, $options.nX + $options.xV, $options.nY + $options.yV, this.scale, deg)
},
// 模拟file 点击事件
dispatchUpload (e) {
this.clearState()
const {file} = this.$options
e.preventDefault()
file.click()
},
// 读取 input file 信息
readFileMsg () {
const {file} = this.$options
const {draw, createImage, $options: {nX, nY}, scale, deg} = this
const wFile = file.files[0]
const reader = new FileReader()
reader.onload = (e) => {
const img = createImage(e.target.result, (img) => {
draw(img, nX, nY, scale, deg)
})
file.value = null
}
reader.readAsDataURL(wFile)
},
// 生成 图像
createImage (src, cb) {
const img = new Image()
this.$el.append(img)
img.className = 'base64-hidden'
img.onload = () => {
cb(img)
}
img.src = src
this.$options.img = img
},
// 操作画布画图
draw (img, x = 0, y = 0, scale = 0.5,deg = Math.PI ) {
const {ctx} = this.$options
let {width, height} = this
// 图片尺寸
let imgW = img.offsetWidth
let imgH = img.offsetHeight
ctx.save()
ctx.clearRect( 0, 0, width, height)
ctx.translate( width / 2, height / 2, img)
ctx.rotate(deg)
ctx.drawImage(img, x, y, imgW * scale, imgH * scale)
ctx.restore()
},
// ... 事件绑定
handleClip (e) {
const {handleMove, $options, deg} = this
if (!$options.img) {
return
}
Object.assign(this.$options, {
x: e.screenX,
y: e.screenY
})
on({
el: window,
type: 'mousemove',
fn: handleMove
})
once({
el: window,
type: 'mouseup',
fn: (e) =>{
console.log('down')
switch (deg) {
case 0: {
Object.assign($options, {
nX: $options.nX + $options.xV,
nY: $options.nY + $options.yV,
xV: 0,
yV: 0
})
break;
}
case Math.PI / 2: {
Object.assign($options, {
nX: $options.nY + $options.yV,
nY: $options.nX - $options.xV,
xV: 0,
yV: 0
})
break;
}
case Math.PI: {
Object.assign($options, {
nX: $options.nX - $options.xV,
nY: $options.nY - $options.yV,
xV: 0,
yV: 0
})
break;
}
default: {
// $options.nY - $options.yV, $options.nX + $options.xV
Object.assign($options, {
nX: $options.nY - $options.yV,
nY: $options.nX + $options.xV,
xV: 0,
yV: 0
})
}
}
off({
el: window,
type: 'mousemove',
fn: handleMove
})
}
})
},
// ... 处理鼠标移动
handleMove (e){
e.preventDefault()
e.stopPropagation()
const {$options, draw, scale, deg} = this
Object.assign($options, {
xV: e.screenX - $options.x,
yV: e.screenY - $options.y
})
switch (deg) {
case 0: {
draw($options.img, $options.nX + $options.xV, $options.nY + $options.yV, scale, deg)
break;
}
case Math.PI / 2: {
draw($options.img, $options.nY + $options.yV, $options.nX - $options.xV, scale, deg)
break;
}
case Math.PI: {
draw($options.img, $options.nX - $options.xV, $options.nY - $options.yV, scale, deg)
break;
}
default: {
draw($options.img, $options.nY - $options.yV, $options.nX + $options.xV, scale, deg)
break;
}
}
},
// 清除状态
clearState () {
const {$options, width, height} = this
if ($options.img) {
this.$el.removeChild($options.img)
Object.assign($options, {
x: 0,
y: 0,
xV: 0,
yV: 0,
nX: -width / 2,
nY: -height / 2,
img: null,
})
}
},
// 输出文件
outFile () {
const {$refs: {ctx}} = this
console.log(ctx.toDataURL())
ctx.toBlob((blob) => {console.log(blob)})
}
}
}
</script>
<style>
@component-namespace jc {
@component clip-image{
position: relative;
width: 100%;
canvas {
position: relative;
width: 100%;
height: 100%;
cursor: pointer;
box-shadow: 0 0 3px #333;
}
input {
display: none;
}
.base64-hidden {
position: absolute;
top: 0;
left: 0;
display: block;
width: 100%;
height: auto;
z-index: -999;
opacity: 0;
}
.clip-scale-btn {
position: relative;
@utils-clearfix;
margin-bottom: 5px;
text-align: center;
a {
float: left;
width: 20px;
height: 20px;
border-radius: 50%;
color: #fff;
background: #49a9ee;
text-align: center;
cursor: pointer;
}
&>.poor, &>.right-rotate {
float: right;
}
&>span{
position: absolute;
z-index: -9;
top: 0;
left: 0;
display: block;
position: relative;
width: 100%;
text-align: center;
height: 20px;
line-height: 20px;
}
}
.upload-warp {
@utils-clearfix;
.upload-btn,.upload-cancel {
float: left;
display:inline-block;
width: 60px;
height: 25px;
line-height: 25px;
color: #fff;
border-radius: 5px;
background: #49a9ee;
box-shadow: 0 0 0 #333;
text-align: center;
top: 0;
left: 0;
right: 0;
bottom: 0;
margin: auto;
cursor: pointer;
margin-top: 5px;
}
.upload-cancel{
background: gray;
float: right;
}
}
.to-send-file {
margin-top: 5px;
display: block;
width: 50px;
height: 25px;
line-height: 25px;
color: #fff;
border-radius: 5px;
background: #49a9ee;
cursor: pointer;
}
}
}
</style>

项目代码（https://github.com/L6zt/vuesrr）