Javascript – Pdfjs rendering is blurrry not same as viewer.html

It seems like a duplicate question but I have searched all those questions on stackoverflow and have not yet found a solution.

I followed up on the document and set up an example here: [https://jsfiddle.net/r2tc9ob5/][1] using the same pdf as in Mozilla’s viewer page (https://mozilla.github.io/pdf.js/web/viewer.html).

<script src="//mozilla.github.io/pdf.js/build/pdf.js"></script>
<h1>PDF.js 'Hello, world!' example</h1>
<canvas id="the-canvas"></canvas>
var url = 'https://mozilla.github.io/pdf.js/web/compressed.tracemonkey-pldi-09.pdf';

// Loaded via <script> tag, create shortcut to access PDF.js exports.
var pdfjsLib = window['pdfjs-dist/build/pdf'];

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

// Asynchronous download of PDF
var loadingTask = pdfjsLib.getDocument(url);
loadingTask.promise.then(function(pdf) {
  console.log('PDF loaded');
  
  // Fetch the first page
  var pageNumber = 1;
  pdf.getPage(pageNumber).then(function(page) {
    console.log('Page loaded');
    
    var scale = 1.5;
    var viewport = page.getViewport({scale: scale});

    // 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.promise.then(function () {
      console.log('Page rendered');
    });
  });
}, function (reason) {
  // PDF loading error
  console.error(reason);
});

It’s clearly that in jsfiddle link, the PDF was displayed blurry, not sharp as in Mozilla’s viewer example.

Any solution is appreciated.

Thank you very much