vue里面使用pdfjs-dist+fabric实现pdf电子签章！！！

最近领导提了一个新需求：仿照e签宝，实现pdf电子签章！
这是做出来的效果图，当然还有很多待修改

然后我就去看了下人家e签宝的操作界面，左侧是印章，右侧是pdf，然后拖拽印章到pdf上面，点击保存，下次打开时显示印章的位置。
思路：我首先想到了拖拽、pdf预览、坐标；分工明确，前端来实现拖拽，pdf预览及把印章信息和坐标传给后端，后端只需要把信息和坐标保存下来就可以了。
之前实现pdf预览就是通过window.open，打开一个窗口，显示pdf，功能很多，但是和需求不符，需要做的事是把pdf显示出来，同时可以可以拖拽印章到上面去，也不要放大与缩小及其他的功能。百度下了，说是用pdfjs-dist，这个pdf插件可以自定义很多的功能，但是实际用起来，发现好坑。。最后去百度了下，vue实现pdf电子签章， 看有没有现成的，然后还真找到了一个。js处理pdf展示、分页和签章等功能，下载到本地(只许查看index.html文件即可)后发现大佬用的不是vue-cli脚手架，是引用的cdn链接，然后就cv到项目里面了，跟着步骤，安装了pdfjs-dist插件(pdf插件)和fabric插件(专门处理印章的插件)这两个插件，但是项目本地运行后，报错了。。

百思不得其解啊，照着步骤来的啊，为啥呢，然后又回去看了下大佬的代码，发现他的pdf.js不是用的pdfjs-dist，而是引入的pdf的cdn链接

然后我就在项目的public/index.html下面引入这个链接

pdf路径则是使用的一个在线的pdf链接，https://www.gjtool.cn/pdfh5/git.pdf，发现可以打开了（样式做了些修改）

开始觉得似乎已经大功告成了，到时候和后端商量下返回数据的格式就完事了的，谁知道还是有问题的。。多次打开关闭pdf后，有时候pdf会不加载出来了。人麻了，然后看了下提示，加载超时了，取消加载。

明显是cdn链接的问题，那就把pdf.js文件下载到本地呗，本地加载快，应该不会出现加载超时的问题，结果还是有问题。

唉，真的是服了，使用cdn链接吧，会加载超时，下载到本地引用吧，又会报这么个莫名其妙的问题，然后今天浏览博客时，发现一个兄弟碰到了一样的问题，哈哈，发现还是引入pdf方式的问题

/* 引用cdn链接，可以使用但会加载超时 */ 
// let pdfjsLib = window["pdfjs-dist/build/pdf"];
// pdfjsLib.GlobalWorkerOptions.workerSrc = 'https://mozilla.github.io/pdf.js/build/pdf.worker.js';
/* 下载到本地，看着官方文档引用，报个莫名其妙的错 */
// import pdfjsLib from 'pdfjs-dist';
// pdfjsLib.GlobalWorkerOptions.workerSrc='pdfjs-dist/build/pdf.worker.js';
/* 下载到本地，照着大佬的方式引用，完美！ */
let pdfjsLib =require("pdfjs-dist/legacy/build/pdf.js");
import workerSrc from "pdfjs-dist/legacy/build/pdf.worker.entry";
pdfjsLib.GlobalWorkerOptions.workerSrc = workerSrc;

这是大佬的博客链接pdf.js 使用攻略及错误集合

不过这项目的电子签章有些与众不同，用户打开的pdf，是可以自定义的，即用户打开弹窗，在tinymac编辑器里面输入内容，然后切换tab，会立即生成一个pdf，接下来才是用户使用电子签章的过程

以下是电子签章的主要代码，和大佬的index.html的代码差不多，就是做了点修改

代码部分

首先 引入pdfjs-dist插件和fabric插件

npm install pdfjs-dist

npm i fabric --save

html部分

<div id="elesign" class="elesign">
	<el-row>
    <el-col :span="4" style="margin-top:1%;">
      <div class="left-title">我的印章</div>
      <draggable v-model="mainImagelist" :group="{ name: 'itext', pull: 'clone' }" :sort="false" @end="end">
        <transition-group type="transition">
          <li v-for="item in mainImagelist" :key="item" class="item" style="text-align:center;">
            <img :src="item" width="100%;" height="100%" class="imgstyle" />
          </li>
        </transition-group>
      </draggable>
    </el-col>
    <el-col :span="16" style="text-align:center;" class="pCenter">
      <div class="page">
        <!-- <el-button class="btn-outline-dark" @click="zoomIn">-</el-button>
        <span style="color:red;">{{(percentage*100).toFixed(0)+'%'}}</span>
        <el-button class="btn-outline-dark" @click="zoomOut">+</el-button> -->
        <el-button class="btn-outline-dark" @click="prevPage">上一页</el-button>
        <el-button class="btn-outline-dark" @click="nextPage">下一页</el-button>
        <el-button class="btn-outline-dark">{{ pageNum }}/{{ numPages }}页</el-button>
        <el-input-number style="margin:0 5px;border-radius:5px;" class="btn-outline-dark"  v-model="pageNum" :min="1" :max="numPages" label="输入页码"></el-input-number>
        <el-button class="btn-outline-dark" @click="cutover">跳转</el-button>
      </div>
      <canvas id="the-canvas" />
      <!-- 盖章部分 -->
      <canvas id="ele-canvas"></canvas>
      <div class="ele-control" style="margin-bottom:2%;">
        <el-button class="btn-outline-dark" @click="removeSignature"> 删除签章</el-button>
        <el-button class="btn-outline-dark" @click="clearSignature"> 清除所有签章</el-button>
        <el-button class="btn-outline-dark" @click="submitSignature">提交所有签章信息</el-button>
      </div>
    </el-col>
    <el-col :span="4" style="margin-top:1%;">
      <div class="left-title">任务信息</div>
      <div style="text-align:center;">
        <div>
          <div class="right-item">
            <div class="right-item-title">文件主题</div>
            <div class="detail-item-desc">{{ taskInfo.title }}</div>
          </div>
          <div class="right-item">
            <div class="right-item-title">发起方</div>
            <div class="detail-item-desc">{{ taskInfo.uname }}</div>
          </div>
          <div class="right-item">
            <div class="right-item-title">截止时间</div>
            <div class="detail-item-desc">{{ taskInfo.endtime }}</div>
          </div>
        </div>
      </div>
    </el-col>
  </el-row>
</div>

js部分

import {fabric} from 'fabric';
let pdfjsLib =require("pdfjs-dist/legacy/build/pdf.js");
import workerSrc from "pdfjs-dist/legacy/build/pdf.worker.entry";
pdfjsLib.GlobalWorkerOptions.workerSrc = workerSrc;
import draggable from "vuedraggable";
export default {
  components: {draggable},
  data() {
    return {
      //pdf预览
      pdfUrl: '',
      pdfDoc: null,
      numPages: 1,
      pageNum: 1,
      scale: 2.2,
      pageRendering: false,
      pageNumPending: null,
      sealUrl: '',
      signUrl: '',
      canvas: null,
      ctx: null,
      canvasEle: null,
      whDatas: null,
      mainImagelist: [],
      taskInfo: {},
    }
  },
  computed: {
      hasSigna() {
        return this.canvasEle && this.canvasEle.getObjects()[0] ? true : false;
      },
  },
  created(){
    var that = this;
    that.mainImagelist = [require('./sign.png'),require('./seal.png')];
    that.taskInfo = {'title':'测试盖章', uname:'张三', endtime:'2021-09-01 17:59:59'};
  },
  methods: {
    //pdf预览
    // zoomIn() {
    //   console.log("缩小");
    //   if(this.scale<=0.5){
    //     this.$message.error("已经显示最小比例")
    //   }else{
    //     this.scale-=0.1;
    //     this.percentage-=0.1;
    //     this.renderPage(this.pageNum);
    //     this.renderFabric();
    //   }
    // },
    // zoomOut() {
    //   console.log("放大")
    //   if(this.scale>=2.2){
    //     this.$message.error('已经显示最大比例')
    //   }else{
    //     this.scale+=0.1;
    //     this.percentage+=0.1;
    //     this.renderPage(this.pageNum);
    //     this.renderFabric();
    //   }
    // },
    renderPage(num) {
      let _this = this;
      this.pageRendering = true;
      return this.pdfDoc.getPage(num).then((page) => {
        let viewport = page.getViewport({ scale: _this.scale });//设置视口大小
        _this.canvas.height = viewport.height;
        _this.canvas.width = viewport.width;
        
        // Render PDF page into canvas context
        let renderContext = {
          canvasContext: _this.ctx,
          viewport: viewport,
        };
        let renderTask = page.render(renderContext);
        // Wait for rendering to finish
        renderTask.promise.then(() => {
          _this.pageRendering = false;
          if (_this.pageNumPending !== null) {
            // New page rendering is pending
            this.renderPage(_this.pageNumPending);
            _this.pageNumPending = null;
          }
        });
      });
    },
    queueRenderPage(num) {
      if (this.pageRendering) {
        this.pageNumPending = num;
      } else {
        this.renderPage(num);
      }
    },
    prevPage() {
      this.confirmSignature();
      if (this.pageNum <= 1) {
        return;
      }
      this.pageNum--;
    },
    nextPage() {
      this.confirmSignature();
      if (this.pageNum >= this.numPages) {
        return;
      }
      this.pageNum++;
    },
    cutover() {
      this.confirmSignature();
    },
    //渲染pdf，到时还会盖章信息，在渲染时，同时显示出来，不应该在切换页码时才显示印章信息
    showpdf(pdfUrl) {
      let caches = JSON.parse(localStorage.getItem('signs')); //获取缓存字符串后转换为对象
      console.log(caches);
      if(caches == null) return false;
      let datas = caches[this.pageNum];
      if(datas != null && datas != undefined) {
        for (let index in datas) {
          this.addSeal(datas[index].sealUrl, datas[index].left, datas[index].top, datas[index].index);
        }
      }
      this.canvas = document.getElementById("the-canvas");
      this.ctx = this.canvas.getContext("2d");
      pdfjsLib.getDocument({url:pdfUrl, rangeChunkSize:65536, disableAutoFetch:false}).promise.then((pdfDoc_) => {
        this.pdfDoc = pdfDoc_;
        this.numPages = this.pdfDoc.numPages;
        this.renderPage(this.pageNum).then(() => {
          this.renderPdf({
            width: this.canvas.width,
            height: this.canvas.height,
          });
        });
        this.commonSign(this.pageNum, true);
      });
    },
    /**
   *  盖章部分开始
   */
    // 设置绘图区域宽高
    renderPdf(data) {
      this.whDatas = data;
      // document.querySelector("#elesign").style.width = data.width + "px";
    },
    // 生成绘图区域
    renderFabric() {
      let canvaEle = document.querySelector("#ele-canvas");
      let pCenter=document.querySelector(".pCenter");
      canvaEle.width = pCenter.clientWidth;
      // canvaEle.height = (this.whDatas.height)*(this.scale);
      canvaEle.height = this.whDatas.height;

      this.canvasEle = new fabric.Canvas(canvaEle);
      let container = document.querySelector(".canvas-container");
      container.style.position = "absolute";
      container.style.top = "50px";
      // container.style.left = "30%";
    },
    // 相关事件操作哟
    canvasEvents() {
      // 拖拽边界 不能将图片拖拽到绘图区域外
      this.canvasEle.on("object:moving", function (e) {
        var obj = e.target;
        // if object is too big ignore
        if(obj.currentHeight > obj.canvas.height || obj.currentWidth > obj.canvas.width){
          return;
        }
        obj.setCoords();
        // top-left  corner
        if(obj.getBoundingRect().top < 0 || obj.getBoundingRect().left < 0){
          obj.top = Math.max(obj.top, obj.top-obj.getBoundingRect().top);
          obj.left = Math.max(obj.left, obj.left-obj.getBoundingRect().left);
        }
        // bot-right corner
        if(obj.getBoundingRect().top+obj.getBoundingRect().height  > obj.canvas.height || obj.getBoundingRect().left+obj.getBoundingRect().width  > obj.canvas.width){
          obj.top = Math.min(obj.top, obj.canvas.height-obj.getBoundingRect().height+obj.top-obj.getBoundingRect().top);
          obj.left = Math.min(obj.left, obj.canvas.width-obj.getBoundingRect().width+obj.left-obj.getBoundingRect().left);
        }
      });
    },
    // 添加公章
    addSeal(sealUrl, left, top, index) {
      fabric.Image.fromURL(
        sealUrl,
        (oImg) => {
          oImg.set({
            left: left,
            top: top,
            // angle: 10,
            scaleX: 0.8,
            scaleY: 0.8,
            index:index,
          });
            // oImg.scale(0.5); //图片缩小一
          this.canvasEle.add(oImg);
        }
      );
    },
    // 删除签章
    removeSignature() {
      this.canvasEle.remove(this.canvasEle.getActiveObject())
    },
    //翻页展示盖章信息
    commonSign(pageNum, isFirst = false) {
      if(isFirst == false) this.canvasEle.remove(this.canvasEle.clear()); //清空页面所有签章
      let caches = JSON.parse(localStorage.getItem('signs')); //获取缓存字符串后转换为对象
      console.log(caches);
      if(caches == null) return false;
      let datas = caches[this.pageNum];
      if(datas != null && datas != undefined) {
        for (let index in datas) {
          this.addSeal(datas[index].sealUrl, datas[index].left, datas[index].top, datas[index].index);
        }
      }
    },
    //确认签章位置并保存到缓存
    confirmSignature() {
      let data = this.canvasEle.getObjects(); //获取当前页面内的所有签章信息
      let caches = JSON.parse(localStorage.getItem('signs')); //获取缓存字符串后转换为对象

      let signDatas = {}; //存储当前页的所有签章信息
      let i = 0;
      // let sealUrl = '';
      for(var val of data) {
        signDatas[i] =  {
          width: val.width,
          height: val.height,
          top: val.top,
          left: val.left,
          angle: val.angle,
          translateX: val.translateX,
          translateY: val.translateY,
          scaleX: val.scaleX,
          scaleY: val.scaleY,
          pageNum: this.pageNum,
          sealUrl: this.mainImagelist[val.index],
          index:val.index
        }
        i++;
      }
      if(caches == null) {
          caches = {};
          caches[this.pageNum] = signDatas;
      } else {
          caches[this.pageNum] = signDatas;
      }
      localStorage.setItem('signs', JSON.stringify(caches)); //对象转字符串后存储到缓存
    },
    //提交数据
    submitSignature() {
        this.confirmSignature();
        let caches = localStorage.getItem('signs');
        console.log(JSON.parse(caches));
        return false
    },
    //清空数据
    clearSignature() {
      this.canvasEle.remove(this.canvasEle.clear()); //清空页面所有签章
      localStorage.removeItem('signs'); //清除缓存
    },
    end(e){
   this.addSeal(this.mainImagelist[e.newDraggableIndex], e.originalEvent.layerX, e.originalEvent.layerY, e.newDraggableIndex)
    },
    //设置PDF预览区域高度
    setPdfArea(){
       this.pdfUrl = 'https://www.gjtool.cn/pdfh5/git.pdf';
       this.pdfurl=res.data.data.pdfurl;
       this.$nextTick(() => {
         this.showpdf(this.pdfUrl);//接口返回的应该还有盖章信息，不只是pdf
       });
    },
  },
},

css部分

<style scoped>

/*pdf部分*/

.pCenter{
  overflow-x: hidden;
}
#the-canvas{
  margin-top:10px;
}

html:fullscreen {
    background: white;
}
.elesign {
    display: flex;
    flex: 1;
    flex-direction: column;
    position: relative;
    /* padding-left: 180px; */
    margin: auto;
    /* width:600px; */
}
.page {
    text-align:center;
    margin:0 auto;
    margin-top: 1%;
}
#ele-canvas {
    /* border: 1px solid #5ea6ef; */
    overflow: hidden;
}
.ele-control {
    text-align: center;
    margin-top: 3%;
}
#page-input {
    width: 7%;
}

@keyframes ani-demo-spin {
    from { transform: rotate(0deg);}
    50% { transform: rotate(180deg);}
    to { transform: rotate(360deg);}
}
/* .loadingclass{
    position: absolute;
    top:30%;
    left:49%;
    z-index: 99;
} */
.left {
    position: absolute;
    top: 42px;
    left: -5px;
    padding: 5px 5px;
    /*border: 1px solid #eee;*/
    /*border-radius: 4px;*/
}
.left-title {
    text-align:center;
    padding-bottom: 10px;
    border-bottom: 1px solid #eee;
}
li {
    list-style-type:none;
    padding: 10px;
}
.imgstyle{
    vertical-align: middle;
    width: 130px;
    border: solid 1px #e8eef2;
    background-image: url("tuo.png");
    background-repeat:no-repeat;
}
.right {
    position: absolute;
    top: 7px;
    right: -177px;
    margin-top: 34px;
    padding-top: 10px;
    padding-bottom: 20px;
    width: 152px;
    /*border: 1px solid #eee;*/
    /*border-radius: 4px;*/
}
.right-item {
    margin-bottom: 15px;
    margin-left: 10px;
}
.right-item-title {
    color: #777;
    height: 20px;
    line-height: 20px;
    font-size: 12px;
    font-weight: 400;
    text-align: left !important;
}
.detail-item-desc {
    color: #333;
    line-height: 20px;
    width: 100%;
    font-size: 12px;
    display: inline-block;
    text-align: left;
}
.btn-outline-dark {
    color: #0f1531;
    background-color: transparent;
    background-image: none;
    border:1px solid #3e4b5b;
}

.btn-outline-dark:hover {
    color: #fff;
    background-color: #3e4b5b;
    border-color: #3e4b5b;
}