之前写了一个上传头像的功能模块，以下的内容是描述上传头像过程中裁剪图片插件结合vue的一个使用。

当然，使用就安装    npm install cropperjs

接着再引入   import Cropper from 'cropperjs'

下面是源码

<template>
  <div id="demo">
    <!-- 遮罩层 -->
    <div class="container" v-show="panel">
      <div>
        <img id="image" :src="url" alt="Picture">
      </div>

      <button type="button" id="button" @click="crop">确定</button>
        
    </div>

    <div style="padding:20px;">
        <div class="show">
          <div class="picture" :style="'backgroundImage:url('+headerImage+')'">
          </div>
        </div>
        <div style="margin-top:20px;">
          <input type="file" id="change" accept="image" @change="change">
          <label for="change"></label>
        </div>
        
    </div>
  </div>
</template>

<script>
import Cropper from 'cropperjs'
export default {
  components: {
    
  },
  data () {
    return {
      headerImage:'',
      picValue:'',
      cropper:'',
      croppable:false,
      panel:false,
      url:''
    }
  },
  mounted () {
    //初始化这个裁剪框
    var self = this;
    var image = document.getElementById('image');
    this.cropper = new Cropper(image, {
      aspectRatio: 1,
      viewMode: 1,
      background:false,
      zoomable:false,
      ready: function () {
        self.croppable = true;
      }
    });
  },
  methods: {
    getObjectURL (file) {
      var url = null ; 
      if (window.createObjectURL!=undefined) { // basic
        url = window.createObjectURL(file) ;
      } else if (window.URL!=undefined) { // mozilla(firefox)
        url = window.URL.createObjectURL(file) ;
      } else if (window.webkitURL!=undefined) { // webkit or chrome
        url = window.webkitURL.createObjectURL(file) ;
      }
      return url ;
    },
    change (e) {
      let files = e.target.files || e.dataTransfer.files;
      if (!files.length) return;
      this.panel = true;
      this.picValue = files[0];
      
      this.url = this.getObjectURL(this.picValue);
      //每次替换图片要重新得到新的url
      if(this.cropper){
        this.cropper.replace(this.url);
      }
      this.panel = true;

    },
    crop () {
        this.panel = false;
        var croppedCanvas;
        var roundedCanvas;

        if (!this.croppable) {
          return;
        }
        // Crop
        croppedCanvas = this.cropper.getCroppedCanvas();
        console.log(this.cropper)
        // Round
        roundedCanvas = this.getRoundedCanvas(croppedCanvas);

        this.headerImage = roundedCanvas.toDataURL();
        this.postImg()
        
    },
    getRoundedCanvas (sourceCanvas) {
      
      var canvas = document.createElement('canvas');
      var context = canvas.getContext('2d');
      var width = sourceCanvas.width;
      var height = sourceCanvas.height;
      
      canvas.width = width;
      canvas.height = height;

      context.imageSmoothingEnabled = true;
      context.drawImage(sourceCanvas, 0, 0, width, height);
      context.globalCompositeOperation = 'destination-in';
      context.beginPath();
      context.arc(width / 2, height / 2, Math.min(width, height) / 2, 0, 2 * Math.PI, true);
      context.fill();

      return canvas;
    },
    postImg () {
      //这边写图片的上传
    }
  }
}
</script>

<style>
*{
  margin: 0;
  padding: 0;
}
#demo #button {
  position: absolute;
  right: 10px;
  top: 10px;
  width: 80px;
  height: 40px;
  border:none;
  border-radius: 5px;
  background:white;
}
#demo .show {
  width: 100px;
  height: 100px;
  overflow: hidden;
  position: relative;
  border-radius: 50%;
  border: 1px solid #d5d5d5;
}
#demo .picture {
  width: 100%;
  height: 100%;
  overflow: hidden;
  background-position: center center;
  background-repeat: no-repeat;
  background-size: cover; 
}
#demo .container {
    z-index: 99;
    position: fixed;
    padding-top: 60px;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
    background:rgba(0,0,0,1);
}

#demo #image {
  max-width: 100%;
}

.cropper-view-box,.cropper-face {
  border-radius: 50%;
}
/*!
 * Cropper.js v1.0.0-rc
 * https://github.com/fengyuanchen/cropperjs
 *
 * Copyright (c) 2017 Fengyuan Chen
 * Released under the MIT license
 *
 * Date: 2017-03-25T12:02:21.062Z
 */

.cropper-container {
  font-size: 0;
  line-height: 0;

  position: relative;

  -webkit-user-select: none;

     -moz-user-select: none;

      -ms-user-select: none;

          user-select: none;

  direction: ltr;
  -ms-touch-action: none;
      touch-action: none
}

.cropper-container img {
  /* Avoid margin top issue (Occur only when margin-top <= -height) */
  display: block;
  min-width: 0 !important;
  max-width: none !important;
  min-height: 0 !important;
  max-height: none !important;
  width: 100%;
  height: 100%;
  image-orientation: 0deg
}

.cropper-wrap-box,
.cropper-canvas,
.cropper-drag-box,
.cropper-crop-box,
.cropper-modal {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
}

.cropper-wrap-box {
  overflow: hidden;
}

.cropper-drag-box {
  opacity: 0;
  background-color: #fff;
}

.cropper-modal {
  opacity: .5;
  background-color: #000;
}

.cropper-view-box {
  display: block;
  overflow: hidden;

  width: 100%;
  height: 100%;

  outline: 1px solid #39f;
  outline-color: rgba(51, 153, 255, 0.75);
}

.cropper-dashed {
  position: absolute;

  display: block;

  opacity: .5;
  border: 0 dashed #eee
}

.cropper-dashed.dashed-h {
  top: 33.33333%;
  left: 0;
  width: 100%;
  height: 33.33333%;
  border-top-width: 1px;
  border-bottom-width: 1px
}

.cropper-dashed.dashed-v {
  top: 0;
  left: 33.33333%;
  width: 33.33333%;
  height: 100%;
  border-right-width: 1px;
  border-left-width: 1px
}

.cropper-center {
  position: absolute;
  top: 50%;
  left: 50%;

  display: block;

  width: 0;
  height: 0;

  opacity: .75
}

.cropper-center:before,
  .cropper-center:after {
  position: absolute;
  display: block;
  content: ' ';
  background-color: #eee
}

.cropper-center:before {
  top: 0;
  left: -3px;
  width: 7px;
  height: 1px
}

.cropper-center:after {
  top: -3px;
  left: 0;
  width: 1px;
  height: 7px
}

.cropper-face,
.cropper-line,
.cropper-point {
  position: absolute;

  display: block;

  width: 100%;
  height: 100%;

  opacity: .1;
}

.cropper-face {
  top: 0;
  left: 0;

  background-color: #fff;
}

.cropper-line {
  background-color: #39f
}

.cropper-line.line-e {
  top: 0;
  right: -3px;
  width: 5px;
  cursor: e-resize
}

.cropper-line.line-n {
  top: -3px;
  left: 0;
  height: 5px;
  cursor: n-resize
}

.cropper-line.line-w {
  top: 0;
  left: -3px;
  width: 5px;
  cursor: w-resize
}

.cropper-line.line-s {
  bottom: -3px;
  left: 0;
  height: 5px;
  cursor: s-resize
}

.cropper-point {
  width: 5px;
  height: 5px;

  opacity: .75;
  background-color: #39f
}

.cropper-point.point-e {
  top: 50%;
  right: -3px;
  margin-top: -3px;
  cursor: e-resize
}

.cropper-point.point-n {
  top: -3px;
  left: 50%;
  margin-left: -3px;
  cursor: n-resize
}

.cropper-point.point-w {
  top: 50%;
  left: -3px;
  margin-top: -3px;
  cursor: w-resize
}

.cropper-point.point-s {
  bottom: -3px;
  left: 50%;
  margin-left: -3px;
  cursor: s-resize
}

.cropper-point.point-ne {
  top: -3px;
  right: -3px;
  cursor: ne-resize
}

.cropper-point.point-nw {
  top: -3px;
  left: -3px;
  cursor: nw-resize
}

.cropper-point.point-sw {
  bottom: -3px;
  left: -3px;
  cursor: sw-resize
}

.cropper-point.point-se {
  right: -3px;
  bottom: -3px;
  width: 20px;
  height: 20px;
  cursor: se-resize;
  opacity: 1
}

@media (min-width: 768px) {

  .cropper-point.point-se {
    width: 15px;
    height: 15px
  }
}

@media (min-width: 992px) {

  .cropper-point.point-se {
    width: 10px;
    height: 10px
  }
}

@media (min-width: 1200px) {

  .cropper-point.point-se {
    width: 5px;
    height: 5px;
    opacity: .75
  }
}

.cropper-point.point-se:before {
  position: absolute;
  right: -50%;
  bottom: -50%;
  display: block;
  width: 200%;
  height: 200%;
  content: ' ';
  opacity: 0;
  background-color: #39f
}

.cropper-invisible {
  opacity: 0;
}

.cropper-bg {
  background-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQAQMAAAAlPW0iAAAAA3NCSVQICAjb4U/gAAAABlBMVEXMzMzTjRV2AAAACXBIWXMAAArrAAAK6wGCiw1aAAAAHHRFWHRTb2Z0d2FyZQBBZG9iZSBGaXJld29ya3MgQ1M26LyyjAAAABFJREFUCJlj+M/AgBVhF/0PAH6/D/HkDxOGAAAAAElFTkSuQmCC');
}

.cropper-hide {
  position: absolute;

  display: block;

  width: 0;
  height: 0;
}

.cropper-hidden {
  display: none !important;
}

.cropper-move {
  cursor: move;
}

.cropper-crop {
  cursor: crosshair;
}

.cropper-disabled .cropper-drag-box,
.cropper-disabled .cropper-face,
.cropper-disabled .cropper-line,
.cropper-disabled .cropper-point {
  cursor: not-allowed;
}


</style>