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前言

最近在做头像上传功能时需要增加一个图片裁剪上传功能，于是找到了VueCropper插件

提示：以下是本篇文章正文内容，下面案例可供参考

一、实现原理是什么？

1.首先我们需要选择一张图片，Vue-cropper会出现一个矩形框供我们框选，裁剪区域的大小和我们的所框的范围相关联,在框选后会获取到相关位置信息及所选图片的信息，获得信息之后将其转为blob格式方便预览，预览之后确认无误点击上传按钮此时再使用formData对象将图片传到服务器上。

效果图： 

二、使用步骤

1.引入插件

代码如下（示例）：

官网：https://github.com/xyxiao001/vue-cropper

npm install vue-cropper 或者 yarn add vue-cropper

2.具体实现

1.封装裁剪上传组件(CropperImage.vue)：

<template>
  <div class="cropper-content">
    <div class="cropper-box">
      <div class="cropper">
        <vue-cropper ref="cropper" :img="option.img" :outputSize="option.outputSize" :outputType="option.outputType" :info="option.info" :canScale="option.canScale" :autoCrop="option.autoCrop" :autoCropWidth="option.autoCropWidth" :autoCropHeight="option.autoCropHeight" :fixed="option.fixed" :fixedNumber="option.fixedNumber" :full="option.full" :fixedBox="option.fixedBox" :canMove="option.canMove" :canMoveBox="option.canMoveBox" :original="option.original" :centerBox="option.centerBox" :height="option.height" :infoTrue="option.infoTrue" :maxImgSize="option.maxImgSize" :enlarge="option.enlarge" :mode="option.mode" @realTime="realTime" @imgLoad="imgLoad">
        </vue-cropper>
      </div>
      <!--底部操作工具按钮-->
      <div class="footer-btn">
        <div class="scope-btn">
          <input type="file" id="uploads" style="position:absolute; clip:rect(0 0 0 0);" accept="image/png, image/jpeg, image/gif, image/jpg" @change="selectImg($event)">
          <el-button size="mini" type="danger" plain icon="el-icon-zoom-in" @click="changeScale(1)">放大</el-button>
          <el-button size="mini" type="danger" plain icon="el-icon-zoom-out" @click="changeScale(-1)">缩小</el-button>
          <el-button size="mini" type="danger" plain @click="rotateLeft">↺ 左旋转</el-button>
          <el-button size="mini" type="danger" plain @click="rotateRight">↻ 右旋转</el-button>
        </div>

      </div>
    </div>
    <!--预览效果图-->
    <div class="show-preview">
      <div class="preview">
        <img :src="previews.url" :style="previews.img">
      </div>
      <div class="upload-btn">
        <label class="btn" for="uploads">选择图片</label>
        <el-button size="mini" type="success" @click="uploadImg()">确认上传 <i class="el-icon-upload"></i></el-button>
      </div>
    </div>
  </div>
</template>

<script>
import { VueCropper } from 'vue-cropper'
import { updateAvatar } from ''//这里为文件上传的接口换成自己的文件
export default {
  name: "CropperImage",
  components: {
    VueCropper
  },
  props: ['Name'],
  data () {
    return {
      name: this.Name,
      resImg: '',
      previews: {},
      option: {
        img: this.Name,             //裁剪图片的地址
        outputSize: 1,       //裁剪生成图片的质量(可选0.1 - 1)
        outputType: 'png',  //裁剪生成图片的格式（jpeg || png || webp）
        info: true,          //图片大小信息
        canScale: true,      //图片是否允许滚轮缩放
        autoCrop: true,      //是否默认生成截图框
        autoCropWidth: 200,  //默认生成截图框宽度
        autoCropHeight: 200, //默认生成截图框高度
        fixed: false,         //是否开启截图框宽高固定比例
        fixedNumber: [1.53, 1], //截图框的宽高比例
        full: false,         //false按原比例裁切图片，不失真
        fixedBox: false,      //固定截图框大小，不允许改变
        canMove: true,      //上传图片是否可以移动
        canMoveBox: true,    //截图框能否拖动
        original: false,     //上传图片按照原始比例渲染
        centerBox: true,    //截图框是否被限制在图片里面
        height: false,        //是否按照设备的dpr 输出等比例图片
        infoTrue: false,     //true为展示真实输出图片宽高，false展示看到的截图框宽高
        maxImgSize: 3000,    //限制图片最大宽度和高度
        enlarge: 1,          //图片根据截图框输出比例倍数
        mode: '340px 300px'  //图片默认渲染方式
      }
    };
  },
  methods: {
    //初始化函数
    imgLoad (msg) {
      console.log("工具初始化函数=====" + msg)
    },
    //图片缩放
    changeScale (num) {
      num = num || 1
      this.$refs.cropper.changeScale(num)
    },
    //向左旋转
    rotateLeft () {
      this.$refs.cropper.rotateLeft()
    },
    //向右旋转
    rotateRight () {
      this.$refs.cropper.rotateRight()
    },
    // //实时预览函数
    realTime (data) {
      let that = this
      that.previews = data
      this.$refs.cropper.getCropBlob(data => {
        this.blobToDataURI(data, function (res) {
          that.previewImg = res
        })
      })
    },
    blobToDataURI (blob, callback) {
      var reader = new FileReader();
      reader.readAsDataURL(blob);
      reader.onload = function (e) {
        callback(e.target.result);
      }
    },
    //选择图片
    selectImg (e) {
      let file = e.target.files[0]
      if (!/\.(jpg|jpeg|png|JPG|PNG)$/.test(e.target.value)) {
        this.$message({
          message: '图片类型要求：jpeg、jpg、png',
          type: "error"
        });
        return false
      }
      //转化为blob
      let reader = new FileReader()
      reader.onload = (e) => {
        let data
        if (typeof e.target.result === 'object') {
          data = window.URL.createObjectURL(new Blob([e.target.result]))
        } else {
          data = e.target.result
        }
        this.option.img = data
      }
      //转化为base64
      reader.readAsDataURL(file)
    },

    base64ImgtoFile (dataurl, filename = 'file') {
      //将base64格式分割：['data:image/png;base64','XXXX']
      const arr = dataurl.split(',')
      // .*？ 表示匹配任意字符到下一个符合条件的字符 刚好匹配到：
      // image/png
      const mime = arr[0].match(/:(.*?);/)[1]  //image/png
      //[image,png] 获取图片类型后缀
      const suffix = mime.split('/')[1] //png
      const bstr = atob(arr[1])   //atob() 方法用于解码使用 base-64 编码的字符串
      let n = bstr.length
      const u8arr = new Uint8Array(n)
      while (n--) {
        u8arr[n] = bstr.charCodeAt(n)
      }
      return new File([u8arr], `${filename}.${suffix}`, {
        type: mime
      })
    },
    
    uploadFile (file) {
      const formData = new FormData();
      formData.append('file', file);
      updateAvatar(formData).then(res => {
        if (res.code == 200) {
          this.$emit('uploadImgSuccess', res.data);
        } else {
          this.$message({
            message: '上传失败',
            type: 'error',
            duration: 1000,
          })
        }
      })
    },
    //上传图片
    uploadImg () {
      this.$refs.cropper.getCropData(data => {
        this.resImg = this.base64ImgtoFile(data)
        this.uploadFile(this.resImg)
      })
    },
  },
}
</script>

<style scoped lang="scss">
.btn {
  outline: none;
  display: inline-block;
  line-height: 1;
  white-space: nowrap;
  cursor: pointer;
  -webkit-appearance: none;
  text-align: center;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
  outline: 0;
  -webkit-transition: 0.1s;
  transition: 0.1s;
  font-weight: 500;
  padding: 8px 15px;
  font-size: 12px;
  border-radius: 3px;
  color: #fff;
  background-color: #409eff;
  border-color: #409eff;
  margin-right: 10px;
}
.cropper-content {
  display: flex;
  display: -webkit-flex;
  justify-content: flex-end;
  .cropper-box {
    flex: 1;
    width: 100%;
    .cropper {
      width: auto;
      height: 300px;
    }
  }

  .show-preview {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: center;
    .preview {
      overflow: hidden;
      height: 200px;
      width: 200px;
      background: #cccccc;
      transform: scale(0.8);
      border-radius: 50%;
    }
  }
}
.footer-btn {
  margin-top: 30px;
  display: flex;
  display: -webkit-flex;
  justify-content: space-around;
  .scope-btn {
    display: flex;
    display: -webkit-flex;
    justify-content: space-between;
    padding-right: 10px;
  }
  .upload-btn {
    flex: 1;
    -webkit-flex: 1;
    display: flex;
    display: -webkit-flex;
    justify-content: center;
  }
}
</style>

2.在页面中引用相关组件

<div class="avatar-uploader">
        <div class="avatar-box">
          <el-avatar :size="40" :src="define.comUrl + formData.headicon" class="avatar" />
          <div class="avatar-hover" @click="uploadPicture(define.comUrl + formData.headicon)">更换</div>
        </div>
      </div>

 <!-- 剪裁组件弹窗 -->
    <el-dialog title="裁剪图片" :visible.sync="cropperModel" width="950px" center>
      <CropperImage :Name="cropperName" @uploadImgSuccess="handleUploadSuccess" ref="child"></CropperImage>
    </el-dialog>

<script>
data () {
cropperModel: false,
cropperName: ''//默认图片参数,
}
 methods: {
handleUploadSuccess (data) {      
    //在此处调文件上传的接口
},
//打开文件裁剪组件，并传入默认参数
uploadPicture (name) {
      this.cropperName = name;
      this.cropperModel = true;
    },
}
</script>

总结

代码写得比较随意，大致思路就是这样。