How to implement pdf adaptive height in vue

Vue.js has become one of the most popular JavaScript frameworks in modern web development. If you are developing a Vue.js application that needs to load PDF files, a common problem you may face is that the height of the PDF component does not adapt like other HTML elements.

In this article, we will explore how to implement an adaptive height PDF viewer component by using a JavaScript library called pdf.js.

What is pdf.js?

pdf.js is an open source JavaScript library developed by Mozilla that can render PDF files directly in the web browser without using plug-ins. The library is written entirely in JavaScript and is based on HTML5 Canvas and Web Workers technology.

pdf.js has many features, including a full PDF renderer, text selection and search, thumbnail previews, and more, and can be easily embedded into any web-based application.

Implementing PDF adaptive height

Now we will explain in detail how to use the pdf.js library to implement a PDF viewer component that adapts to the height of its parent container.

Install pdf.js

To use pdf.js, you first need to add it to your Vue.js project. You can install pdf.js using npm by executing the following command.

npm install pdfjs-dist

Create PDF component

In your Vue.js project, create a new component named PDFViewer:

<template>
  <div class="pdf-container">
    <canvas ref="canvas" class="pdf-canvas"></canvas>
  </div>
</template>

<script>
import pdfjsLib from 'pdfjs-dist'

export default {
  name: 'PDFViewer',
  props: {
    src: { type: String, required: true }
  },
  data() {
    return {
      pageNum: 1,
      totalPages: null,
      pdfDoc: null,
    }
  },
  mounted() {
    this.loadPDF()
  },
  methods: {
    async loadPDF() {
      try {
        const loadingTask = pdfjsLib.getDocument(this.src)
        const pdf = await loadingTask.promise

        this.pdfDoc = pdf
        this.totalPages = pdf.numPages

        this.renderPage(this.pageNum)
      } catch (error) {
        console.log(error)
      }
    },
    async renderPage(num) {
      const canvas = this.$refs.canvas
      const ctx = canvas.getContext('2d')

      const page = await this.pdfDoc.getPage(num)

      const viewport = page.getViewport({ scale: 1 })
      const clientWidth = this.$el.clientWidth
      const scale = clientWidth / viewport.width

      const viewportScaled = page.getViewport({ scale })
      canvas.height = viewportScaled.height

      await page.render({
        canvasContext: ctx,
        viewport: viewportScaled
      })
    }
  }
}
</script>

In this PDFViewer component, we use The most important function is the pdfjsLib.getDocument(src) function, which loads a PDF document from the provided URL and returns a Document object. We also define a variable called pageNum to store the page number we wish to display, and a variable called totalPages to store the total number of pages in the PDF document.

In the mounted lifecycle hook of the component, we call the loadPDF method to load the PDF document and start rendering the first page. Additionally, we use the canvas element to render PDF pages. To ensure that the PDF document fits the size of the container, we also use the getBoundingClientRect() method in the Web API to dynamically calculate the height of the canvas element.

Render PDF page

In the renderPage method of the component, we use the getPage method of pdf.js to obtain relevant information of the specified page. We then use the getViewport method to get the view state of the PDF page and use the width of the current container to calculate the zoom factor. Finally, we use the render method to render the page into the canvas element.

Implement adaptive height

To implement adaptive height of the PDF viewer component, we need to dynamically set the height of the canvas element when rendering the PDF page so that it matches the height of the page.

.pdf-canvas {
  width: 100%;
  height: auto;
  max-height: 100%;
}

Please note that in the above CSS style, we set the height of the canvas element to auto, which will ensure that the height of the canvas element is proportional to its width. We then limit the maximum height of the canvas element to the height of its parent element by using the max-height attribute. This will ensure that the height of the PDF page does not exceed the height of the component's container.

Using PDF Viewer Component

Now, we have created a PDF viewer component named PDFViewer and implemented the adaptive height function. For Vue.js applications that need to load PDF files, we can now use the component in the following way:

<template>
  <div class="pdf-viewer-container">
    <PDFViewer :src="pdfUrl" />
  </div>
</template>

<script>
import PDFViewer from '@/components/PDFViewer.vue'

export default {
  components: { PDFViewer },
  data() {
    return {
      pdfUrl: 'path/to/your/pdf/file.pdf'
    }
  }
}
</script>

In the above code example, we add the PDFViewer component to the template of the Vue.js application, And pass the URL of the PDF file to the component as a prop.

Summary

In this article, we learned how to use pdf.js to create a Vue.js PDF viewer component and implement the adaptive height function. By using pdf.js, we can easily embed PDF files into web applications without using plugins or other third-party tools.

Please note that when using pdf.js to render large PDF files, it may affect the performance and load time of your web application. Therefore, when using the methods described in this article, you should consider using techniques such as lazy loading to optimize the loading and rendering process of PDF files.

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