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vue使用pdf-dist实现pdf预览以及水印添加

作者：菜鸟书生

这篇文章主要为大家详细介绍了vue如何使用pdf-dist实现pdf预览以及水印添加的功能，文中的示例代码讲解详细，感兴趣的小伙伴可以跟随小编一起学习一下

一.使用pdf-dist插件将PDF文件转换为一张张canvas图片

npm install pdf-dist

二.页面引入插件

const pdfJS = require("pdfjs-dist");
pdfJS.GlobalWorkerOptions.workerSrc = require("pdfjs-dist/build/pdf.worker.entry");

三.渲染PDF

// 根据页码渲染相应的PDF
renderPage(num) {
  this.renderingPage = true;
  this.pdfData.promise.then((pdf) => {

    this.pdfPageNumber = pdf.numPages;

    pdf.getPage(num).then((page) => {
      // 获取DOM中为预览PDF准备好的canvasDOM对象
      let canvas = this.$refs.myCanvas;
      let ctx = canvas.getContext("2d");

      // 获取页面比率
      let ratio = this._getRatio(ctx);
      
      // 根据页面宽度和视口宽度的比率就是内容区的放大比率
      let dialogWidth = this.$refs["canvasCont"].offsetWidth;
      let pageWidth = page.view[2] * ratio;
      let scale = dialogWidth / pageWidth;
      let viewport = page.getViewport({ scale });
      

      // 记录内容区宽高，后期添加水印时需要
      this.width = viewport.width * ratio;
      this.height = viewport.height * ratio;

      canvas.width = this.width;
      canvas.height = this.height;

      // 缩放比率
      ctx.setTransform(ratio, 0, 0, ratio, 0, 0);

      let renderContext = {
        canvasContext: ctx,
        viewport: viewport,
      };
      page.render(renderContext).promise.then(() => {
        this.renderingPage = false;
        this.pageNo = num;

        // 添加水印
        this._renderWatermark();
      });
    });
  });
},
// 计算角度
_getRatio(ctx) {
  let dpr = window.devicePixelRatio || 1;
  let bsr =
    ctx.webkitBackingStorePixelRatio ||
    ctx.mozBackingStorePixelRatio ||
    ctx.msBackingStorePixelRatio ||
    ctx.oBackingStorePixelRatio ||
    ctx.backingStorePixelRatio ||
    1;
  return dpr / bsr;
},

四.添加水印

// 生成水印图片
_initWatermark() {
  let canvas = document.createElement("canvas");
  canvas.width = 200;
  canvas.height = 200;
  let ctx = canvas.getContext("2d");
  ctx.rotate((-18 * Math.PI) / 180);
  ctx.font = "10px Vedana";
  ctx.fillStyle = "rgba(0, 0, 0, 0.8)";
  ctx.textAlign = "left";
  ctx.textBaseline = "middle";
  ctx.fillText(this.watermark, 10, 100);
  return canvas;
},

五.完整代码（带翻页）

<template>
  <div class="main-container">
    <input type="file" ref="fielinput" @change="uploadFile" />
    <div ref="canvasCont" class="canvas-container">
      <canvas ref="myCanvas" class="pdf-container"></canvas>
    </div>
    <div class="pagination-wrapper">
      <button @click="clickPre">上一页</button>
      <span>第{{ pageNo }} / {{ pdfPageNumber }}页</span>
      <button @click="clickNext">下一页</button>
    </div>
  </div>
</template>
 
<script>
const pdfJS = require("pdfjs-dist");
 
pdfJS.GlobalWorkerOptions.workerSrc = require("pdfjs-dist/build/pdf.worker.entry");
export default {
  props: {
    watermark: {
      type: String,
      default: "水印文字水印文字水印文字",
    },
  },
  mounted() {},
  data() {
    return {
      pageNo: null,
      pdfPageNumber: null,
      renderingPage: false,
      pdfData: null, // PDF的base64
      scale: 1, // 缩放值
      width: "",
      height: "",
    };
  },
  methods: {
    uploadFile() {
      let inputDom = this.$refs.fielinput;
      let file = inputDom.files[0];
      let reader = new FileReader();
      reader.readAsDataURL(file);
      reader.onload = () => {
        let data = atob(
          reader.result.substring(reader.result.indexOf(",") + 1)
        );
        this.loadPdfData(data);
      };
    },
    loadPdfData(data) {
      // 引入pdf.js的字体
      let CMAP_URL = "https://unpkg.com/pdfjs-dist@2.0.943/cmaps/";
      //读取base64的pdf流文件
      this.pdfData = pdfJS.getDocument({
        data: data, // PDF base64编码
        cMapUrl: CMAP_URL,
        cMapPacked: true,
      });
      this.renderPage(1);
    },
 
    // 根据页码渲染相应的PDF
    renderPage(num) {
      this.renderingPage = true;
      this.pdfData.promise.then((pdf) => {

        this.pdfPageNumber = pdf.numPages;
 
        pdf.getPage(num).then((page) => {
          // 获取DOM中为预览PDF准备好的canvasDOM对象
          let canvas = this.$refs.myCanvas;
          let ctx = canvas.getContext("2d");
 
          // 获取页面比率
          let ratio = this._getRatio(ctx);
          
          // 根据页面宽度和视口宽度的比率就是内容区的放大比率
          let dialogWidth = this.$refs["canvasCont"].offsetWidth;
          let pageWidth = page.view[2] * ratio;
          let scale = dialogWidth / pageWidth;
          let viewport = page.getViewport({ scale });
          

          // 记录内容区宽高，后期添加水印时需要
          this.width = viewport.width * ratio;
          this.height = viewport.height * ratio;
 
          canvas.width = this.width;
          canvas.height = this.height;
 
          // 缩放比率
          ctx.setTransform(ratio, 0, 0, ratio, 0, 0);
 
          let renderContext = {
            canvasContext: ctx,
            viewport: viewport,
          };
          page.render(renderContext).promise.then(() => {
            this.renderingPage = false;
            this.pageNo = num;
 
            // 添加水印
            this._renderWatermark();
          });
        });
      });
    },
    // 计算角度
    _getRatio(ctx) {
      let dpr = window.devicePixelRatio || 1;
      let bsr =
        ctx.webkitBackingStorePixelRatio ||
        ctx.mozBackingStorePixelRatio ||
        ctx.msBackingStorePixelRatio ||
        ctx.oBackingStorePixelRatio ||
        ctx.backingStorePixelRatio ||
        1;
      return dpr / bsr;
    },
 
    // 在画布上渲染水印
    _renderWatermark() {
      let canvas = this.$refs.myCanvas;
      let ctx = canvas.getContext("2d");
      // 平铺水印
      let pattern = ctx.createPattern(this._initWatermark(), "repeat");
      ctx.rect(0, 0, this.width, this.height);
      ctx.fillStyle = pattern;
      ctx.fill();
    },
 
    // 生成水印图片
    _initWatermark() {
      let canvas = document.createElement("canvas");
      canvas.width = 200;
      canvas.height = 200;
      let ctx = canvas.getContext("2d");
      ctx.rotate((-18 * Math.PI) / 180);
      ctx.font = "10px Vedana";
      ctx.fillStyle = "rgba(0, 0, 0, 0.8)";
      ctx.textAlign = "left";
      ctx.textBaseline = "middle";
      ctx.fillText(this.watermark, 10, 100);
      return canvas;
    },
 
    clickPre() {
      if (!this.renderingPage && this.pageNo && this.pageNo > 1) {
        this.renderPage(this.pageNo - 1);
      }
    },
    clickNext() {
      if (
        !this.renderingPage &&
        this.pdfPageNumber &&
        this.pageNo &&
        this.pageNo < this.pdfPageNumber
      ) {
        this.renderPage(this.pageNo + 1);
      }
    },
  },
};
</script>
 
<style scoped>
.main-container {
  display: flex;
  flex-direction: column;
  align-items: center;
}
.canvas-container {
  width: 100%;
  height: 100%;
  border: 1px dashed black;
  position: relative;
  display: flex;
  justify-content: center;
}
.pdf-container {
  width: 100%;
  height: 100%;
}
 
.pagination-wrapper {
  display: flex;
  justify-content: center;
  align-items: center;
}
</style>

六.完整代码（滑动）

<template>
  <div class="main-container">
    <input type="file" ref="fielinput" @change="uploadFile" />
    <div ref="canvasCont" class="canvas-container">
      <canvas v-for="pageIndex in pdfPageNumber" 
        :ref="`myCanvas${pageIndex}`" :key="pageIndex" class="pdf-container"></canvas>
    </div>
  </div>
</template>
 
<script>
const pdfJS = require("pdfjs-dist");
 
pdfJS.GlobalWorkerOptions.workerSrc = require("pdfjs-dist/build/pdf.worker.entry");
export default {
  props: {
    watermark: {
      type: String,
      default: "水印文字水印文字水印文字",
    },
  },
  mounted() {},
  data() {
    return {
      pageNo: null,
      pdfPageNumber: null,
      renderingPage: false,
      pdfData: null, // PDF的base64
      scale: 1, // 缩放值
      width: "",
      height: "",
    };
  },
  methods: {
    uploadFile() {
      let inputDom = this.$refs.fielinput;
      let file = inputDom.files[0];
      let reader = new FileReader();
      reader.readAsDataURL(file);
      reader.onload = () => {
        let data = atob(
          reader.result.substring(reader.result.indexOf(",") + 1)
        );
        this.loadPdfData(data);
      };
    },
    loadPdfData(data) {
      // 引入pdf.js的字体
      let CMAP_URL = "https://unpkg.com/pdfjs-dist@2.0.943/cmaps/";
      //读取base64的pdf流文件
      this.pdfData = pdfJS.getDocument({
        data: data, // PDF base64编码
        cMapUrl: CMAP_URL,
        cMapPacked: true,
      });
      this.renderPage(1);
    },
 
    // 根据页码渲染相应的PDF
    renderPage(num) {
      this.renderingPage = true;
      this.pdfData.promise.then((pdf) => {

        this.pdfPageNumber = pdf.numPages;
 
        pdf.getPage(num).then((page) => {
          // 获取DOM中为预览PDF准备好的canvasDOM对象
          let canvas = this.$refs[`myCanvas${num}`][0];
          let ctx = canvas.getContext("2d");
 
          // 获取页面比率
          let ratio = this._getRatio(ctx);
          
          // 根据页面宽度和视口宽度的比率就是内容区的放大比率
          let dialogWidth = this.$refs["canvasCont"].offsetWidth;
          let pageWidth = page.view[2] * ratio;
          let scale = dialogWidth / pageWidth;
          let viewport = page.getViewport({ scale });
          

          // 记录内容区宽高，后期添加水印时需要
          this.width = viewport.width * ratio;
          this.height = viewport.height * ratio;
 
          canvas.width = this.width;
          canvas.height = this.height;
 
          // 缩放比率
          ctx.setTransform(ratio, 0, 0, ratio, 0, 0);
 
          let renderContext = {
            canvasContext: ctx,
            viewport: viewport,
          };
         
          page.render(renderContext).promise.then(() => {
            this.renderingPage = false;
            this.pageNo = num;
            // 添加水印
            this._renderWatermark(num);
            if(num < this.pdfPageNumber){
              this.renderPage(num+1)
            }
          });
        });
      });
    },
    // 计算角度
    _getRatio(ctx) {
      let dpr = window.devicePixelRatio || 1;
      let bsr =
        ctx.webkitBackingStorePixelRatio ||
        ctx.mozBackingStorePixelRatio ||
        ctx.msBackingStorePixelRatio ||
        ctx.oBackingStorePixelRatio ||
        ctx.backingStorePixelRatio ||
        1;
      return dpr / bsr;
    },
 
    // 在画布上渲染水印
    _renderWatermark(num) {
      let canvas = this.$refs[`myCanvas${num}`][0];
      let ctx = canvas.getContext("2d");
      // 平铺水印
      let pattern = ctx.createPattern(this._initWatermark(), "repeat");
      ctx.rect(0, 0, this.width, this.height);
      ctx.fillStyle = pattern;
      ctx.fill();
    },
 
    // 生成水印图片
    _initWatermark() {
      let canvas = document.createElement("canvas");
      canvas.width = 200;
      canvas.height = 200;
      let ctx = canvas.getContext("2d");
      ctx.rotate((-18 * Math.PI) / 180);
      ctx.font = "10px Vedana";
      ctx.fillStyle = "rgba(0, 0, 0, 0.8)";
      ctx.textAlign = "left";
      ctx.textBaseline = "middle";
      ctx.fillText(this.watermark, 10, 100);
      return canvas;
    },
  },
};
</script>
 
<style scoped>
.main-container {
  display: flex;
  flex-direction: column;
  align-items: center;
}
.canvas-container {
  width: 100%;
  height: 100%;
  border: 1px dashed black;
  position: relative;
  /* display: flex; */
  /* justify-content: center; */
}
.pdf-container {
  width: 100%;
  height: 100%;
}
</style>

到此这篇关于vue使用pdf-dist实现pdf预览以及水印添加的文章就介绍到这了,更多相关vue pdf预览内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！

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