PDF.js 'Hello, world!' example

HTML

<script src="//mozilla.github.io/pdf.js/build/pdf.js"></script>

<h1>PDF.js 'Hello, world!' example</h1>
<div id="text-overlay"></div>
<canvas id="the-canvas"></canvas>

CSS

#the-canvas {
  border:1px solid black;
}

#text-overlay {
  box-shadow: 0 1px 3px #444;
  position: absolute;
  font-size: 1px;
  line-height: 1;
}

span {
  position: absolute;
  cursor: text;
  white-space: pre;
  transform-origin: left bottom;
}

JavaScript

// If absolute URL from the remote server is provided, configure the CORS
// header on that server.
var url = '//cdn.mozilla.net/pdfjs/helloworld.pdf';

// Disable workers to avoid yet another cross-origin issue (workers need
// the URL of the script to be loaded, and dynamically loading a cross-origin
// script does not work).
// PDFJS.disableWorker = true;

// The workerSrc property shall be specified.
PDFJS.workerSrc = '//mozilla.github.io/pdf.js/build/pdf.worker.js';

CanvasRenderingContext2D.prototype.strokeText = function () { };
CanvasRenderingContext2D.prototype.fillText = function () { };

// Asynchronous download of PDF
var loadingTask = PDFJS.getDocument(url);
loadingTask.promise.then(function(pdf) {
  var ctx = document.createElement('canvas').getContext('2d', { alpha: false });

  pdf.getPage(1).then(function (page) {
    var viewport = page.getViewport(1.5);

    // Prepare canvas using PDF page dimensions
    var canvas = document.getElementById('the-canvas');
    var context = canvas.getContext('2d');
    canvas.height = viewport.height;
    canvas.width = viewport.width;

    // Render PDF page into canvas context
    var renderContext = {
      canvasContext: context,
      viewport: viewport
    };
    var renderTask = page.render(renderContext);
    renderTask.then(function () {
      console.log('Page rendered');
    });

    var pageContainer = document.getElementById('text-overlay');
    pageContainer.classList.add('page-container');
    pageContainer.style.width = viewport.width + 'px';
    pageContainer.style.height = viewport.height + 'px';

    page.getTextContent({ normalizeWhitespace: true }).then(function (textContent) {
      textContent.items.forEach(function (textItem) {
        var tx = PDFJS.Util.transform(
          PDFJS.Util.transform(viewport.transform, textItem.transform),
          [1, 0, 0, -1, 0, 0]
        );

        var style = textContent.styles[textItem.fontName];

        // adjust for font ascent/descent
       ...