vue 裁剪图片，插件Cropper的使用

全局安装    npm install cropperjs

如果想本项目安装，方便移植：   import Cropper from 'cropperjs'   --save    这样的话，本地 package.json  文件中 dependencies 就会引入  移植后npm install安装就会带入

接着再引入   import Cropper from 'cropperjs'

<template>
<div id="cropper">
            <!-- 遮罩层 -->
            <div class="container" v-show="panel">
                <div><img id="image" :src="url"></div>
                <button type="button" id="button" @click="crop">确定</button>
            </div>
            <!-- 遮罩层 -->

            <div>
                <div class="show">
                    <div class="picture" :style="'backgroundImage:url('+headerImage+')'">
                    </div>
                </div>
                <div>
                    <input type="file" accept="image" @change="change">
                </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: ,
      viewMode: ,
      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[];  

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

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

<style>
*{
  margin: ;
  padding: ;
}
#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: %;
  border: 1px solid #d5d5d5;
}
#demo .picture {
  width: %;
  height: %;
  overflow: hidden;
  background-position: center center;
  background-repeat: no-repeat;
  background-size: cover;
}
#demo .container {
    z-index: ;
    position: fixed;
    padding-top: 60px;
    left: ;
    top: ;
    right: ;
    bottom: ;
    background:rgba(,,,);
}  

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

.cropper-view-box,.cropper-face {
  border-radius: %;
}
/*!
 * 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: ;
  line-height: ;  

  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:  !important;
  max-width: none !important;
  min-height:  !important;
  max-height: none !important;
  width: %;
  height: %;
  image-orientation: 0deg
}  

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

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

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

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

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

  width: %;
  height: %;  

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

.cropper-dashed {
  position: absolute;  

  display: block;  

  opacity: .;
  border:  dashed #eee
}  

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

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

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

  display: block;  

  width: ;
  height: ;  

  opacity: .
}  

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

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

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

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

  display: block;  

  width: %;
  height: %;  

  opacity: .;
}  

.cropper-face {
  top: ;
  left: ;  

  background-color: #fff;
}  

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

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

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

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

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

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

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

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

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

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

.cropper-point.point-s {
  bottom: -3px;
  left: %;
  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:
}  

@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: .
  }
}  

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

.cropper-invisible {
  opacity: ;
}  

.cropper-bg {
  background-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQAQMAAAAlPW0iAAAAA3NCSVQICAjb4U/gAAAABlBMVEXMzMz////TjRV2AAAACXBIWXMAAArrAAAK6wGCiw1aAAAAHHRFWHRTb2Z0d2FyZQBBZG9iZSBGaXJld29ya3MgQ1M26LyyjAAAABFJREFUCJlj+M/AgBVhF/0PAH6/D/HkDxOGAAAAAElFTkSuQmCC');
}  

.cropper-hide {
  position: absolute;  

  display: block;  

  width: ;
  height: ;
}  

.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>  

参考 ：http://blog.csdn.net/xiaogezl/article/details/70227025