Vue3前端h5移动端页面预览PDF使用pdfjs-dist，添加自定义文本水印

pdfjs-dist版本

pnpm i pdfjs-dist@2.5.207

import {ref, onMounted, watch} from 'vue'import { useRoute } from "vue-router";import * as pdfjsLib from 'pdfjs-dist'const route = useRoute()// ！pdfjsLib.GlobalWorkerOptions.workerSrc = new URL('pdfjs-dist/build/pdf.worker.js', import.meta.url).hrefconst numPages = ref(0) // pdf一共多少页const nums = ref(1) // 循环加载的参数const currentNum = ref(1) // 当前页数const jumpNum = ref(1)  // 输入框需要跳转的页数const inpDisabled = ref(true) // pad文件没有加载完所有页数则禁用const imgSrcList = ref([]) // 存储paf每一页const watermarkPoint = [  [-120, -66], [-120, 66], [120, -66], [120, 66]] // 水印坐标let pageHeight = null // 每一页高度let pdfWrap = nulllet isChangeCurrentNum = falseconst query = new URLSearchParams(route.fullPath.split('?')[1]) // 从url地址栏获取水印文本信息const watermarkText = query.get('text') // 自定义的水印文本// url为pdf链接const loadingTask = pdfjsLib.getDocument(query.get('url'))// dom加载之后onMounted(() => {  pdfWrap = document.getElementById('pdf')  togglePage(nums.value)})watch(() => nums.value, (num) => {  if (num     togglePage(num)  } else {    inpDisabled.value = false  }})async function togglePage(pageNumber = 1) {  loadingTask.promise.then(function(pdf) {    numPages.value = pdf.numPages    pdf.getPage(pageNumber).then((page) = {      const scale = 0.1 // 关键！如果清晰度不行，慢慢调整这个数值。      let viewport = page.getViewport({ scale });      let scaleViewport = page.getViewport({ scale: window.screen.width / viewport.width });      let canvas = document.createElement('canvas');      let context = canvas.getContext('2d');      canvas.width = scaleViewport.width;      canvas.height = scaleViewport.height;// 只赋值一次      !pageHeight && (pageHeight = (scaleViewport.height * scale).toFixed(2))      let renderContext = {        canvasContext: context,        viewport: scaleViewport,      };      let renderTask = page.render(renderContext);      renderTask.promise.then(() => {      // 设置自定义文本样式        context.font = `${16 / scale}px Microsoft Yahei`;        context.fillStyle = 'rgba(0, 0, 0, .1)'        context.textAlign = 'center'        context.textBaseline = 'middle'// 设置自定义文本位于每一页pdf的空间位置        watermarkPoint.forEach(point => {          context.translate( ((scaleViewport.width * scale / 2) + point[0]) / scale, ((scaleViewport.height * scale / 2) + point[1]) / scale )          context.rotate(-30 * Math.PI / 180)          context.fillText(watermarkText, 0, 0)          context.resetTransform()        })// 导出canvas图片到图片列表，循环渲染        imgSrcList.value.push(canvas.toDataURL('img/png'))        nums.value++      });    });  }, function (reason) {    console.error(reason);  });}function goToPage(num) {  pdfWrap.scrollTo(0, num === 1 ? 0 : pageHeight * num - pageHeight)  currentNum.value = num  isChangeCurrentNum = true}function handleScroll(e) {  if (!isChangeCurrentNum) {    const current = e.target.scrollTop / pageHeight    currentNum.value = Math.ceil(current === 0 ? 1 : current)  }  isChangeCurrentNum = false}function handleBeforePage() {  currentNum.value = currentNum.value - 1   currentNum.value = currentNum.value + 1 = numPages.value ? numPages.value : currentNum.value + 1  goToPage(currentNum.value)  isChangeCurrentNum = true}                                        {{ currentNum }}          /          {{ numPages }}                                                        跳转  页                    确定                文件正在加载中..跳转功能暂不可用                            .operation-box {  height: 60px;  display: flex;  align-items: center;  justify-content: center;  .operation {    display: flex;    align-items: center;    justify-content: space-around;    background-color: #404040;    width: 100%;    color: #fff;    padding: 10px 20px;    border-radius: 30px;    box-sizing: border-box;    .jump-box {      flex: 1;      font-size: 14px;      display: flex;      align-items: center;      justify-content: center;      .inp-box {        margin-right: 5px;      }    }    .tips {      flex: 1;      text-align: center;      font-size: 14px;    }    .page-num-info {      display: flex;      justify-content: center;      align-items: center;      font-size: 14px;    }    .page-num-info, .home {      width: 60px;      text-align: center;    }  }}