reference error: PDFJS is not defined when loading a pdf - javascript

I am trying to use pdf.js to load pdf into a web application so that I can further extract information from the pdf file live. But I am getting this error with a very minimal example.
I have tried wrapping the code in $(document).ready() as suggested in Uncaught ReferenceError: PDFJS is not defined when initialising PDF.JS
I am not able to access PDFJS in console either.
Below is the code I am using (from https://www.sitepoint.com/custom-pdf-rendering/)
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"/>
<title>PDF.js Learning</title>
</head>
<body>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script type="text/javascript" src="https://mozilla.github.io/pdf.js/build/pdf.js"></script>
<script type="text/javascript" src="https://mozilla.github.io/pdf.js/build/pdf.worker.js"></script>
<script>
$(document).ready(function () {
var url = "https://github.com/mozilla/pdf.js/blob/master/web/compressed.tracemonkey-pldi-09.pdf";
// Asynchronous download PDF
PDFJS.getDocument(url)
.then(function(pdf) {
return pdf.getPage(1);
})
.then(function(page) {
// Set scale (zoom) level
var scale = 1.5;
// Get viewport (dimensions)
var viewport = page.getViewport(scale);
// Get canvas#the-canvas
var canvas = document.getElementById('the-canvas');
// Fetch canvas' 2d context
var context = canvas.getContext('2d');
// Set dimensions to Canvas
canvas.height = viewport.height;
canvas.width = viewport.width;
// Prepare object needed by render method
var renderContext = {
canvasContext: context,
viewport: viewport
};
// Render PDF page
page.render(renderContext);
});
})
</script>
<canvas id='the-canvas'></canvas>
</body>
</html>

pdfjsLib.getDocument() works. Now I just need to know why...

Related

How to display data from response in html canvas

I am trying to display a response fetched from an api in a html canvas, but for some reason the canvas does not display the text from the response. I inspected the element I can see in the dev tools that the data is displayed in the html but I can't see it on the screen, why is the data not visible and how can I display it properly in the canvas?
Here is my html:
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<canvas id="canvas"></canvas>
<script src="js/main.js"></script>
</body>
</html>
and my js:
var canvas = document.getElementById('canvas');
ctx = canvas.getContext('2d');
canvas.width = 934;
canvas.height = 622;
var background = new Image();
background.src = 'assets/background.jpg';
background.onload = function () {
ctx.drawImage(background, 0, 0);
}
fetch('https://api/list')
.then(response => response.json())
.then(data => canvas.innerHTML = data.animals.name[0]);
I tried to display it using the fillText() method but it didn't work as well.
You have to use fillText method to draw text. And also, you made a typo. You have to use the context ctx where as you used the element canvas.
Change the line canvas.innerHTML = data.animals.name[0] to ctx.fillText(data.animals.name[0], 10, 50)

TypeError: myCanvas.getContext is not a function - .PDF implementation

I am trying to implement a .PDF file to my website with mozilla pdfjs-dist.
This is my Script:
<html>
<head>
<script src="https://cdn.jsdelivr.net/npm/pdfjs-dist#2.0.943/build/pdf.min.js"></script>
</head>
<body>
<canvas id="addjob_pdf_preview"></canvas>
</body>
</html>
<script>
pdfjsLib.getDocument("PDFFILELINK").then(doc => {
doc.getPage(1).then(page => {
var myCanvas = document.getElementById("addjob_pdf_preview");
var context = myCanvas.getContext("2d");
var viewport = page.getViewport(1);
myCanvas.width = viewport.width;
myCanvas.height = viewport.height;
page.render({
canvasContext: context,
viewport: viewport
});
});
});
</script>
It throws this error:
TypeError: myCanvas.getContext is not a function
I build the implementation exactly after this tutorial: PDF.js Tutorial
I found a few threads about this topic, but im not able to understand what is wrong.
Some referred to the canvas API explanation: Canvas API
Which lead up to more questions than answers.
Regards

PDF.js 2.0.943 is not rendering PDF in browser

I am trying to display PDF in browser, I found library PDF.js which is most popular and most suggested library. Documentations and are clear, but one I try to use latest official release 2.0.943 document is not rendered, it gets loaded(as I see correct number of pages), but not visible.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
</head>
<body>
<!--<script src="//mozilla.github.io/pdf.js/build/pdf.js"></script>-->
<script src="https://cdn.jsdelivr.net/npm/pdfjs-dist#2.0.943/build/pdf.js"></script>
<h1>PDF.js Previous/Next example</h1>
<div>
<button id="prev">Previous</button>
<button id="next">Next</button>
<span>Page: <span id="page_num"></span> / <span id="page_count"></span></span>
</div>
<canvas id="the-canvas"></canvas>
<script>
$(document).ready(function () {
var pdfData = atob(
'JVBERi0xLjcKCjEgMCBvYmogICUgZW50cnkgcG9pbnQKPDwKICAvVHlwZSAvQ2F0YWxvZwog' +
'IC9QYWdlcyAyIDAgUgo+PgplbmRvYmoKCjIgMCBvYmoKPDwKICAvVHlwZSAvUGFnZXMKICAv' +
'TWVkaWFCb3ggWyAwIDAgMjAwIDIwMCBdCiAgL0NvdW50IDEKICAvS2lkcyBbIDMgMCBSIF0K' +
'Pj4KZW5kb2JqCgozIDAgb2JqCjw8CiAgL1R5cGUgL1BhZ2UKICAvUGFyZW50IDIgMCBSCiAg' +
'L1Jlc291cmNlcyA8PAogICAgL0ZvbnQgPDwKICAgICAgL0YxIDQgMCBSIAogICAgPj4KICA+' +
'PgogIC9Db250ZW50cyA1IDAgUgo+PgplbmRvYmoKCjQgMCBvYmoKPDwKICAvVHlwZSAvRm9u' +
'dAogIC9TdWJ0eXBlIC9UeXBlMQogIC9CYXNlRm9udCAvVGltZXMtUm9tYW4KPj4KZW5kb2Jq' +
'Cgo1IDAgb2JqICAlIHBhZ2UgY29udGVudAo8PAogIC9MZW5ndGggNDQKPj4Kc3RyZWFtCkJU' +
'CjcwIDUwIFRECi9GMSAxMiBUZgooSGVsbG8sIHdvcmxkISkgVGoKRVQKZW5kc3RyZWFtCmVu' +
'ZG9iagoKeHJlZgowIDYKMDAwMDAwMDAwMCA2NTUzNSBmIAowMDAwMDAwMDEwIDAwMDAwIG4g' +
'CjAwMDAwMDAwNzkgMDAwMDAgbiAKMDAwMDAwMDE3MyAwMDAwMCBuIAowMDAwMDAwMzAxIDAw' +
'MDAwIG4gCjAwMDAwMDAzODAgMDAwMDAgbiAKdHJhaWxlcgo8PAogIC9TaXplIDYKICAvUm9v' +
'dCAxIDAgUgo+PgpzdGFydHhyZWYKNDkyCiUlRU9G');
// 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 = 'https://cdn.jsdelivr.net/npm/pdfjs-dist#2.0.943/build/pdf.worker.js';
//pdfjsLib.GlobalWorkerOptions.workerSrc = '//mozilla.github.io/pdf.js/build/pdf.worker.js';
// Using DocumentInitParameters object to load binary data.
var loadingTask = pdfjsLib.getDocument({ data: pdfData });
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);
});
});
</script>
</body>
</html>
Official example fiddle: https://jsfiddle.net/pdfjs/wagvs9Lf/?utm_source=website&utm_medium=embed&utm_campaign=wagvs9Lf
My fiddle with minor change(only version): https://jsfiddle.net/94x2ozbq/
From what I figured out: var viewport = page.getViewport({ scale: scale }) returns object with height and width equal to NaN
You need to make a slight modification to the following line in renderPage(), which in current versions takes an object, but in 2.0.943 is expecting a number:
From:
var viewport = page.getViewport({scale: scale});
To:
var viewport = page.getViewport(scale);

Convert a PDF to thumbnail using PDF.JS

I am trying to write some code that converts the first page of a PDF to a PNG thumbnail. I have found several examples here on stackoverflow and other place on the web and it seems like a simple thing to do, but I cannot make it work.
I have a HTML file that looks like this
<!DOCTYPE html>
<html>
<head>
<title>JR PDF test</title>
</head>
<body>
<script type="text/javascript" src="/build/pdf.js"></script>
<script type="text/javascript" src="jr-pdf.js"></script>
<script type="text/javascript" src="canvas2image.js"></script>
</body>
<div id="pdf-main-container">
<a id="download-image" href="#">Download PNG</a>
</div>
</div>
</html>
<canvas id="the-canvas"></canvas>
and a the jr-pdf.js looks like this
// URL of PDF document
var url = "REGLEMENT_FOR_RALLY_2012.pdf";
// Asynchronous download PDF
PDFJS.getDocument(url)
.then(function(pdf) {
return pdf.getPage(1);
})
.then(function(page) {
// Set scale (zoom) level
var scale = 1.5;
// Get viewport (dimensions)
var viewport = page.getViewport(scale);
// Get canvas#the-canvas
var canvas = document.getElementById('the-canvas');
// Fetch canvas' 2d context
var context = canvas.getContext('2d');
// Set dimensions to Canvas
canvas.height = viewport.height;
canvas.width = viewport.width;
// Prepare object needed by render method
var renderContext = {
canvasContext: context,
viewport: viewport
};
// Render PDF page
page.render(renderContext);
// JR experiments
console.log('hej');
url = canvas.toDataURL();
downloadButton = document.getElementById('download-image');
downloadButton.setAttribute('download', 'jr.png');
downloadButton.setAttribute('href', url);
});
The first page of the PDF file is rendered correctly to the screen and a jr.png file is generated. When I look at the PNG file the header seems right, but when I try to view the file with an image viewer it is empty (actually it is shown as transparent).
So I guess these lines are wrong:
url = canvas.toDataURL();
downloadButton = document.getElementById('download-image');
downloadButton.setAttribute('download', 'jr.png');
downloadButton.setAttribute('href', url);
Any suggestions on how to make a correct PNG file?
page.render is asynchronous function -- you need to wait until it finishes painting
var renderTask = page.render(renderContext);
renderTask.promise.then(function () {
// use canvas now
var url = canvas.toDataURL();
var downloadButton = document.getElementById('download-image');
downloadButton.setAttribute('download', 'jr.png');
downloadButton.setAttribute('href', url);
});

How to set BPG on background

Can I use a BPG image as a <div> or <body> background? background: url('bg.bpg'); doesn't work.
There is a Javascript decoder which allows .bpg images to be displayed in <img> tags, but I want to use one as a <body> background.
The Javascript BPG decoder works by converting the source .bpg file into an ImageData object, which can then be drawn to a canvas. So all you need to do is get the canvas as a PNG data string and set that as the body background image:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>BPG background example.</title>
<!-- Decoder script from http://bellard.org/bpg/ -->
<script src="bpgdec8a.js"></script>
<script>
"use strict";
function setBackground(filename)
{
// Create a hidden canvas with the same dimensions as the image.
var canvas = document.createElement("canvas");
canvas.style.visibility = "hidden";
canvas.width = 512;
canvas.height = 512;
document.body.appendChild(canvas);
// Create a drawing context and a BPG decoder.
var ctx = canvas.getContext("2d");
var img = new BPGDecoder(ctx);
// Attempt to load the image.
img.onload = function()
{
// Once the image is ready, draw it to the canvas...
ctx.putImageData(this.imageData, 0, 0);
// ...and copy the canvas to the body background.
document.body.style.background = "url('" + canvas.toDataURL("image/png") + "')";
};
img.load(filename);
}
</script>
</head>
<body onload="setBackground('lena512color.bpg');">
<p>Hello, World!</p>
</body>
</html>

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