Generating thumbnail of a pdf using PDF.js

Question

I would like to generate a thumbnail from a pdf file using PDF.js, but it isn't like anothers js that have just one file and all needed to include the js in your project is to write:

<script src="any.js"></script>

How can I use PDF.js in my project? I'm using PHP in backend.

Answer 1

Based on helloworld example:

function makeThumb(page) {
  // draw page to fit into 96x96 canvas
  var vp = page.getViewport(1);
  var canvas = document.createElement("canvas");
  canvas.width = canvas.height = 96;
  var scale = Math.min(canvas.width / vp.width, canvas.height / vp.height);
  return page.render({canvasContext: canvas.getContext("2d"), viewport: page.getViewport(scale)}).promise.then(function () {
    return canvas;
  });
}

pdfjsLib.getDocument("https://raw.githubusercontent.com/mozilla/pdf.js/ba2edeae/web/compressed.tracemonkey-pldi-09.pdf").promise.then(function (doc) {
  var pages = []; while (pages.length < doc.numPages) pages.push(pages.length + 1);
  return Promise.all(pages.map(function (num) {
    // create a div for each page and build a small canvas for it
    var div = document.createElement("div");
    document.body.appendChild(div);
    return doc.getPage(num).then(makeThumb)
      .then(function (canvas) {
        div.appendChild(canvas);
    });
  }));
}).catch(console.error);

<script src="//npmcdn.com/pdfjs-dist/build/pdf.js"></script>

Answer 2

I figured it out, the scale is not a parameter. The parameters are an object with field of scale that needed to be set.

function makeThumb(page) {
    // draw page to fit into 96x96 canvas
    var vp = page.getViewport({ scale: 1, });
    var canvas = document.createElement("canvas");
    var scalesize = 1;
    canvas.width = vp.width * scalesize;
    canvas.height = vp.height * scalesize;
    var scale = Math.min(canvas.width / vp.width, canvas.height / vp.height);
    console.log(vp.width, vp.height, scale);
    return page.render({ canvasContext: canvas.getContext("2d"), viewport: page.getViewport({ scale: scale }) }).promise.then(function () {
        return canvas; 
    });
}