vue实现裁切图片同时实现放大、缩小、旋转功能

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

<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;
      }
    }

项目代码：https://github.com/L6zt/vuesrr

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持呐喊教程。

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