实现PDF加水印以及自定义水印样式

<template><div><button @click="previewHandle">预览</button><button @click="downFileHandle">下载</button><el-input v-model="watermarkText" /><el-input v-model.number="watermarkrotate" /><iframe id="log_frame" class="log-iframe" frameborder="0" :src="pdfPreviewUrl"></iframe></div>
</template><script setup>
import { ref, reactive, onMounted } from 'vue'
import { degrees, PDFDocument, rgb, StandardFonts } from "pdf-lib";
import fontkit from '@pdf-lib/fontkit'const pdfFileEnd = ref('http://111.229.162.189:8003/file/construction/2024_01_08/三高共管对接接口(5)_14ba6d68.pdf')
const pdfPreviewBlob = ref()
const pdfPreviewUrl = ref('/pdf/web/viewer.html?file=http://111.229.162.189:8003/file/construction/2024_01_08/三高共管对接接口(5)_14ba6d68.pdf')const watermarkText = ref('2024-01-17') // 水印文字
const watermarkrotate = ref(45) // 水印旋转角度// PDF 下载
const addWatermark = async (rotate) => {/*2.获取pdf文件的arrarybuffer文件流可请求后台接口返回的base64文件流，然后转成arrayBuffer类型可访问前端项目中的本地文件，不能直接访问服务器链接文件，会有跨域问题*/try {// 1.通过url获取pdf文件的arrarybuffer文件流const existingPdfBytes = await fetch(pdfFileEnd.value).then((res) => res.arrayBuffer());// 2.将arraybuffer数据转成pdf文档const pdfDoc = await PDFDocument.load(existingPdfBytes);// 3.1  内置字体（不支持中文）, 如果水印中不包含中文可直接用内置字体(不支持中文)// const fontkitFile = await pdfDoc.embedFont(StandardFonts.Helvetica);// 3.2 自定义字体，如不需要使用自定义字体可以将这一段全部注释掉，也不用下载自定义字体文件和自定义字体工具fontkit// 将自己下载好的.ttf文件放置项目中，然后访问文件路径(不支持访问本地文件)// const fontBytes = await fetch("@/assets/DS-DIGIT.TTF").then((res) => res.arrayBuffer());// pdfDoc.registerFontkit(fontkit); // 自定义字体挂载、fontkit为自定义字体注册工具// const fontkitFile = await pdfDoc.embedFont(fontBytes);//  4. 为每页pdf添加文字水印const pages = pdfDoc.getPages();for (let i = 0; i < pages.length; i++) {const noPage = pages[i];const { width, height } = noPage.getSize();for (let i = 0; i < 10; i++) {for (let j = 0; j < 3; j++) {noPage.drawText(watermarkText.value, {x: 230 * j + 36,y: (height / 4) * i + 20,size: 20,// font: fontkitFile, //字体（内置/自定义）color: rgb(0.46, 0.53, 0.6),rotate: degrees(rotate),opacity: 0.3,});}}}//5. 保存pdf文件的unit64Arrary文件流const pdfBytes = await pdfDoc.save();pdfPreviewBlob.value = pdfBytes// const blob = new Blob([pdfBytes], { type: 'application/pdf' });// const url = window.URL.createObjectURL(blob);// pdfPreviewUrl.value = '/pdf/web/viewer.html?file=' + url// saveByteArray("水印PDF.pdf", pdfBytes);} catch (error) {console.log("文件下载失败！");}
}
// 预览文件
const previewHandle = async () => {console.log(typeof(watermarkrotate.value));await addWatermark(watermarkrotate.value)const blob = new Blob([pdfPreviewBlob.value], { type: 'application/pdf' });const url = window.URL.createObjectURL(blob);pdfPreviewUrl.value = '/pdf/web/viewer.html?file=' + url
}
// 下载文件
const downFileHandle = () => {var blob = new Blob([pdfPreviewBlob.value], { type: "application/pdf" });var link = document.createElement("a");link.href = window.URL.createObjectURL(blob);link.download = '水印pdf';link.click();
}onMounted(() => {addWatermark()
})
</script><style lang="scss" scoped>
.log-iframe {width: 800px;height: 520px;
}
</style>