今天把进行了实战；再vue中；写完整了这个功能；

• 拖动盖章；
• pdf预览；

• 生成x,y轴坐标；
  最初位置如下：

  
  
  image.png
  
  
  image.png

<style lang="scss">
    .helpCenter{
        background-color:#fff; 
        .center {
            position: relative;
            text-align: center;
            padding-top: 20px;
            background: #fff;
        }
        .sign-wrap{
            position: absolute;
            .sign-img{
             position: relative;
            }
        }
    }
    .helpCenter .pdfBtn{
        width: 1200px;
        margin: 0 auto;
        background-color: #fff;
        text-align: center;
        margin-bottom:10px; 
        button{
            cursor: pointer;
            width: 100px;
            height: 30px;
        }
    }
    .main{
       display: flex;
       justify-content: center;
    }
    .side-bar{
       .side-barinfo{
           width:300px;
           height: 100vh;
           border: 1px solid #fa0;
       } 
       .signbutton{
        cursor: pointer;
       }
       
    }
    .sign-img{
           z-index: 18;
       }
       .sign-imginner{
           width: 200px;
           height: 200px;
           background: url('../../static/icon_pxi.png') center center;
           background-size: 200px 200px;
           z-index: 18;
        //    display: none;
       }
</style>
<template>
<div class="helpCenter" v-loading="!isready">
    <div class="main" v-show="isready">
        <div class="side-bar">
            <h2>推拽章的信息</h2>
            <div class="side-barinfo">
                <div class="signbutton">推动盖章</div>
                <div class="sign-img" @mousedown='signPic' @mouseup='removeSignPic'>
                    <div class="sign-imginner">
                     <h2 style="color:#fff;text-align:center;">章托放</h2>
                    </div>
                    <!-- <img src="" style="width:200px;height:200px;" alt=""> -->
                </div>
            </div>
            
        </div>
         <div class="center">
             <div class="sign-wrap" @mousedown='signPic' @mouseup='removeSignPic'></div>
            <canvas style="border:1px solid #f00" ref='canvasDOM' class="canvasstyle" id="the-canvas"></canvas>
        </div>
    </div>
     <div class="pdfBtn">
            <button type="primary" @click="prev"><i class="el-icon-arrow-left el-icon--left"></i>上一页</button>
            <span>Page: <span v-text="page_num"></span> / <span v-text="page_count"></span></span>
            <button type="primary" @click="next">下一页<i class="el-icon-arrow-right el-icon--right"></i></button>
            <input type="text" v-model='gotopage_num' style="width:100px;height:29px;" placeholder="请输入页数">
            <button @click="goTopage">确定</button>
            <button @click="downpdf">下载</button>
        </div>
</div>
</template>
<script>
import PDFJS from '../../static/pdf/pdf.js';
export default {
    name: "helpCenter",
    data() {
        return {
            pdfurl:'https://yunlian-ku-res-cloudwarehouse-prod.oss-cn-beijing.aliyuncs.com/cloudwarehouse/oss/contract/chb-help-20180920.pdf?OSSAccessKeyId=LTAIgsIfRCwojpcm&Expires=1570500208&Signature=CBpZntWfITvsm6zCGGl765Z1am8%3D&time='+Date.now(),//pdf链接地址
            pdfDoc: null, //pdfjs 生成的对象
            pageNum: 1, //
            pageRendering: false,
            pageNumPending: null,
            compuscale:1, //放大倍数
            scale:1.6,//放大倍数
            page_num: 0, //当前页数
            page_count: 0, //总页数
            gotopage_num:'',//跳转到指定的页面
            // maxscale: 2, //最大放大倍数
            // minscale: 0.8, //最小放大倍数
            isready: false
        };
    },
    created() {
        var root = "$Urlhttp";
        if (root != "/ssocorp") {
            this.ajaxUrl = "";
        }
        var root2 = "$webRoot";
        if (root2 == "/api") {
            this.ajaxUrl2 = "/api";
        } else if (root2 != "/testca") {
            this.ajaxUrl2 = "";
        };
    },
     methods: {
            signPic(e){
                document.addEventListener("mousemove",this.signmouseMve,false);
            },
            removeSignPic(e){
                let signPicdom=document.querySelector(".sign-img");
                let scrollTop = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop;
                console.log(e);
                console.dir(signPicdom);
                console.log('scrollTop:',scrollTop)
                console.dir(this.$refs.canvasDOM);
                let perX=(this.getOffsetLeft(signPicdom)-this.getOffsetLeft(this.$refs.canvasDOM))/this.$refs.canvasDOM.clientWidth;
                let perY=(this.getOffsetTop(signPicdom)-this.getOffsetTop(this.$refs.canvasDOM)+scrollTop+21)/this.$refs.canvasDOM.clientHeight;
                let signWraphtml=document.querySelector('.sign-wrap');
                signWraphtml.style.top=this.$refs.canvasDOM.clientHeight*perY+'px';
                signWraphtml.style.left=this.$refs.canvasDOM.clientWidth*perX+'px';
                signWraphtml.appendChild(signPicdom.firstChild);
                document.removeEventListener('mousemove',this.signmouseMve,false);
                console.log({perX:parseInt(perX*100)+'%',perY:parseInt(perY*100)+'%'});
                return {perX:perX,perY:perY};//获取到最后的位置；反出来；
            },
            signmouseMve(e){
                var signPicdom=document.querySelector(".sign-img");
                if(!(document.querySelector('.sign-wrap').firstChild===null)){
                 signPicdom.appendChild(document.querySelector('.sign-wrap').firstChild);
                }
                var ev=e||event;
                signPicdom.style.position='fixed';
                signPicdom.style.top=(this.getPos(ev).y-signPicdom.clientHeight/2)+'px';
                signPicdom.style.left=(this.getPos(ev).x-signPicdom.clientWidth/2)+'px';
            },
            getPos(ev){
                let scrollTop=document.documentElement.scrollTop||document.body.scrollTop;
                let scrollLeft=document.documentElement.scrollLeft||document.body.scrollLeft;
                return {x: ev.clientX, y: ev.clientY};
            },
            getOffsetLeft(obj){
              var tmp = obj.offsetLeft;
              var val = obj.offsetParent;
              while(val != null){
              tmp += val.offsetLeft;
                val = val.offsetParent;
               }
             return tmp;
            },
            getOffsetTop(obj){
               var tmp = obj.offsetTop;
               var val = obj.offsetParent;
             while(val != null){
                tmp += val.offsetTop;
               val = val.offsetParent;
               }
                return tmp;
             },
            downpdf(){//下载pdf
                window.open(this.pdfurl);
            },
            renderPage(num) { //渲染pdf
                let vm = this
                this.pageRendering = true;
                let canvas = document.getElementById('the-canvas')
                    // Using promise to fetch the page
                this.pdfDoc.getPage(num).then(function(page) {
                    var viewport = page.getViewport(vm.compuscale);
                    //alert(vm.canvas.height)
                    canvas.height = viewport.height;
                    canvas.width = viewport.width;

                    // Render PDF page into canvas context
                    vm.isready = true
                    var renderContext = {
                        canvasContext: vm.ctx,
                        viewport: viewport
                    };
                    var renderTask = page.render(renderContext);

                    // Wait for rendering to finish
                    renderTask.promise.then(function() {
                        vm.pageRendering = false;
                        if (vm.pageNumPending !== null) {
                            // New page rendering is pending
                            vm.renderPage(vm.pageNumPending);
                            vm.pageNumPending = null;
                        }
                    });
                });
                vm.page_num = vm.pageNum;

            },
            addscale() { //放大
                if (this.compuscale >= this.maxscale) {
                    return
                }
                this.compuscale += 0.1;
                this.queueRenderPage(this.pageNum)
            },
            minus() { //缩小
                if (this.compuscale <= this.minscale) {
                    return
                }
                this.compuscale -= 0.1;
                this.queueRenderPage(this.pageNum)
            },
            prev() { //上一页
                let vm = this
                if (vm.pageNum <= 1) {
                    return;
                }
                vm.pageNum--;
                vm.queueRenderPage(vm.pageNum);
            },
            next() { //下一页
                let vm = this
                if (vm.pageNum >= vm.page_count) {
                    return;
                }
                vm.pageNum++;
                vm.queueRenderPage(vm.pageNum);
            },
            //跳转到指定的页
            goTopage(){
                var that=this;
                if(Number.isNaN(that.gotopage_num/1)){
                    this.$message.error("请输入数字");
                    this.gotopage_num='';
                    return;
                }
                if(this.gotopage_num<1||this.gotopage_num>this.page_count){
                    this.gotopage_num='';
                    this.$message.error("请输入范围内的页码");
                    return;
                };
                this.pageNum=this.gotopage_num;
                this.queueRenderPage(that.gotopage_num);
            },
            closepdf() { //关闭PDF
                this.pageNum = 1;
                this.pdfDoc = null;
                this.isready = false
                this.compuscale = this.scale
                this.$emit('closepdf')
            },
            throwerr(err) {
                this.$emit('pdferr', err);
            },
            queueRenderPage(num) {
                var a=parseInt(num)
                console.log(a);
                if (this.pageRendering) {
                    this.pageNumPending = a;
                } else {
                    this.renderPage(a);
                }
            }
        },
        computed: {
            ctx() {
                let id = document.getElementById('the-canvas')
                return id.getContext('2d');
            },
            isshowpdf() {
                if (this.value == undefined) return false
                return this.value;
            }
        },
        mounted() {
            this.compuscale = this.scale;
            let vm = this
            var val = vm.pdfurl
            if (val == '' || val == undefined) return
            PDFJS.getDocument(val).then(function(pdfDoc_) { //初始化pdf
                vm.pdfDoc = pdfDoc_;
                vm.page_count = vm.pdfDoc.numPages
                vm.renderPage(vm.pageNum);
            }).catch(function(err) {
                if (err) {
                    console.log(err)
                    vm.throwerr(vm.pdfurl)
                }
            })
        },
};
</script>
<!-- Add "scoped" attribute to limit CSS to this component only -->

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