I've a problem to convert canvas to img..
What's the best approach to use toDataURL() and insert it in img src?
when I launch the script it gives me the correct canvas but the img is blank..
this is my code:
<!DOCTYPE HTML>
<html>
<head>
<script type='text/javascript' src='//code.jquery.com/jquery-2.2.3.js'></script>
<script type="text/javascript" src="https://raw.github.com/mozilla/pdf.js/gh-pages/build/pdf.js"></script>
</head>
<body>
<div id='anteprima' ></div>
<div id='anteprima_img' ></div>
<script type="text/javascript">
var file = 'http://www.businessmodelgeneration.com/downloads/businessmodelgeneration_preview.pdf';
pdftoimg(file, 1, 0.5, 'anteprima');
function pdftoimg(file, num, scale2, idd) {
PDFJS.disableWorker = true;
PDFJS.getDocument(file).then(function(pdf) {
pdf.getPage(num).then(function(page) {
var canvas = document.createElement('canvas');
canvas.id = 'pag' + num;
canvas.className = 'grande';
canvasContainer = document.getElementById(idd);
var context = canvas.getContext('2d');
var viewport = page.getViewport(scale2);
canvas.height = viewport.height;
canvas.width = viewport.width;
var renderContext = {
canvasContext: context,
viewport: viewport
};
page.render(renderContext);
canvasContainer.appendChild(canvas);
var dataUrl = canvas.toDataURL();
image = document.createElement('img');
image.src = dataUrl;
$('#anteprima_img').html(image);
});
});
};
</script>
</body>
</html>
Your code is perfectly fine, you need to just wait for render canvas before converting it to data URL.
page.render(renderContext).then(function(){
// code for converting data url
});
<!DOCTYPE HTML>
<html>
<head>
<script type='text/javascript' src='//code.jquery.com/jquery-2.2.3.js'></script>
<script type="text/javascript" src="https://raw.github.com/mozilla/pdf.js/gh-pages/build/pdf.js"></script>
</head>
<body>
<div id='anteprima' ></div>
<div id='anteprima_img' ></div>
<script type="text/javascript">
var file = 'http://www.businessmodelgeneration.com/downloads/businessmodelgeneration_preview.pdf';
pdftoimg(file, 1, 0.5, 'anteprima');
function pdftoimg(file, num, scale2, idd) {
PDFJS.disableWorker = true;
PDFJS.getDocument(file).then(function(pdf) {
pdf.getPage(num).then(function(page) {
var canvas = document.createElement('canvas');
canvas.id = 'pag' + num;
canvas.className = 'grande';
canvasContainer = document.getElementById(idd);
var context = canvas.getContext('2d');
var viewport = page.getViewport(scale2);
canvas.height = viewport.height;
canvas.width = viewport.width;
var renderContext = {
canvasContext: context,
viewport: viewport
};
page.render(renderContext).then(function(){
canvasContainer.appendChild(canvas);
var dataUrl = canvas.toDataURL();
image = document.createElement('img');
image.src = dataUrl;
$('#anteprima_img').html(image);
});
});
});
};
</script>
</body>
</html>
Related
I am trying to generate a PDF document from a HTML document sing an input and a pre loaded image in my javascript code, here are the codes:
<html>
<head>
<title>
Generar pdf
</title>
</head>
<body>
<input type = "text" id = "jjj">
<button id="button" onclick="generar();"></button>
<script src = "jsPDF-1.3.2/dist/jspdf.debug.js"></script>
<script src = "pdf.js"></script>
</body>
</html>
Javascript
var input = document.getElementById('jjj');
var pdf = new jsPDF();
function generar(){
var texto = input.value;
var imgData = 'https://docs.gimp.org/es/images/tutorials/quickie-jpeg-
100.jpg';
pdf.addImage(imgData, 'JPG', 15, 40, 180, 160);
pdf.text(30, 30, texto);
pdf.save('my_pdf.pdf');
}
And it won't work. It worked with jsut the text, but not the Image. Anyone help, would be very appreciated.
you cannot use direct image url. you need to convert image to base64 and then add it in pdf. Also, using external image will generate error in Chrome / Firefox due to Cross origin request.
Below is the complete code:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
<input type = "text" id = "jjj">
<button id="button" onclick="genratePDF();"></button>
<script src = "jspdf.debug.js"></script>
<script src = "jspdf.min.js"></script>
<script>
var input = document.getElementById('jjj');
// var imgData = 'https://docs.gimp.org/es/images/tutorials/quickie-jpeg-100.jpg';
var imgData = 'testimg.jpg';
function genratePDF() {
getDataUri(imgData, function (dataUri) {
generar(dataUri);
});
}
function getDataUri(url, cb)
{
var image = new Image();
image.onload = function () {
var canvas = document.createElement('canvas');
canvas.width = this.naturalWidth;
canvas.height = this.naturalHeight;
//next three lines for white background in case png has a transparent background
var ctx = canvas.getContext('2d');
ctx.fillStyle = '#fff'; /// set white fill style
ctx.fillRect(0, 0, canvas.width, canvas.height);
canvas.getContext('2d').drawImage(this, 0, 0);
cb(canvas.toDataURL('image/jpeg'));
};
image.src = url;
}
function generar(img) {
var texto = input.value;
var pdf = new jsPDF();
pdf.addImage(img, 'JPG', 15, 40, 100, 100);
pdf.text(30, 30, texto);
pdf.save('my_pdf.pdf');
}
</script>
</body>
</html>
Main Changes are getDataUri() ; this function generates base64 image of your provided image. And then in Callback it triggers the generar() to generate PDF
function getDataUri(url, cb)
{
var image = new Image();
image.onload = function () {
var canvas = document.createElement('canvas');
canvas.width = this.naturalWidth;
canvas.height = this.naturalHeight;
//next three lines for white background in case png has a transparent background
var ctx = canvas.getContext('2d');
ctx.fillStyle = '#fff'; /// set white fill style
ctx.fillRect(0, 0, canvas.width, canvas.height);
canvas.getContext('2d').drawImage(this, 0, 0);
cb(canvas.toDataURL('image/jpeg'));
};
image.src = url;
}
this SO question helps me in this solution Convert a image url to pdf using jspdf
I am trying to use waveform.js found on http://www.waveformjs.org to draw waveforms of SoundCloud tracks. It hasn't been working so I've stripped down waveform.js to a bare bones form that attempts to draw a fillRect in a newly created canvas element through a Waveform object. The canvas element is successfully created but the fillRect does not appear. I've contrasted this to the direct creation of a canvas element and fillRect, which both work.
Here is the HTML:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Sample document</title>
</head>
<body>
<div id="example1"></div>
<hr>
<div id="example2"></div>
</body>
<script src="waveform.js"></script>
<script src="script.js"></script>
</html>
Here is script.js:
var canvas, container;
// Creating canvas element and rect in example1
canvas = document.createElement("canvas");
canvas.setAttribute("id", "canvas");
container = document.getElementById("example1");
container.appendChild(canvas);
canvas.width = container.clientWidth;
canvas.height = container.clientHeight;
var c = document.getElementById("canvas");
var ctx = c.getContext("2d");
ctx.fillRect(20,20,50,100);
// Both created successfully
// Creating canvas element and rect in example2, through waveform object
var waveform = new Waveform({
container: document.getElementById("example2")
});
// Canvas element created successfully, no rectangle
Here is waveform.js:
(function() {
var Waveform;
window.Waveform = Waveform = (function() {
Waveform.name = 'Waveform';
function Waveform(options) {
this.container = options.container;
this.canvas = this.createCanvas(this.container, this.container.clientWidth, this.container.clientHeight);
this.context = this.canvas.getContext("2d");
this.width = parseInt(this.context.canvas.width, 10);
this.height = parseInt(this.context.canvas.height, 10);
this.makeRect();
};
Waveform.prototype.createCanvas = function(container, width, height) {
var canvas;
canvas = document.createElement("canvas");
canvas.setAttribute("id", "wfCanvas");
container.appendChild(canvas);
canvas.width = width;
canvas.height = height;
return canvas;
};
Waveform.prototype.makeRect = function() {
var wfCanvas = document.getElementById("wfCanvas");
var ctx = wfCanvas.getContext("2d");
ctx.fillRect(20,20,50,100);
}
return Waveform;
})();
}).call(this);
Bruh you're way over doing it.
Just be sure that the container you are applying the waveform to has PIXEL DIMENSIONS defined as either css or inline.
Why does nothing show up on the canvas? The picture is in the same folder as the code, I've tried to directly copy some code, and just change the sources, it still doesn't work. That leads me to believe, that it is not a fault in the actual way I draw the picture, but in the way I load the canvas?
I can add other stuff to the canvas, just not pictures.
<!DOCTYPE html>
<head></head>
<body>
<script>
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.height = 500;
canvas.width = 800;
document.body.appendChild(canvas);
var imag = new Image();
imag.onload = function() {
context.drawImage(imageObj, 0, 0);
};
imag.src = "underwater.png";
</script>
</body>
You most likely copied this code from somewhere and forgot to change the image object name
<!DOCTYPE html>
<head></head>
<body>
<script>
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.height = 500;
canvas.width = 800;
document.body.appendChild(canvas);
var imag = new Image();
imag.onload = function() {
context.drawImage(imag, 0, 0);
};
imag.src = "underwater.png";
</script>
</body>
This picture will not draw to the canvas. It is being loaded and I see it when body.appendChild(img); is called. Does anyone had an idea why it is not showing in canvas? I'm following the code example from the html5 course on udacity. Thank you for any help!
<!DOCTYPE html>
<html>
<head>
<title>First Game</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<link type="text/css" rel="stylesheet" href="TestCanvasCSS.css"/>
</head>
<body id="body">
<script>
var canvas;
var ctx = null;
var img = null;
var body = null;
setup = function() {
body = document.getElementById("body");
canvas = document.createElement("canvas");
ctx = canvas.getContext('2d');
//canvas.setAttribute("class","canvasMain");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
body.appendChild(canvas);
img = new Image();
img.onload = onImageLoad();
img.src = 'http://www.html5canvastutorials.com/demos/assets/darth-vader.jpg';
};
onImageLoad = function() {
console.log("Image has loaded");
body.appendChild(img);
ctx.drawImage(img, 0, 0);
};
setup();
</script>
<!-- <script type="text/javascript" src="TestCanvas.js"> </script> -->
</body>
</html>
img.onload = onImageLoad;
not onImageLoad(); you're executing the function if you include the parenthesis
I have this simple code for draw an image in a canvas but it's work only in Firefox
this is the code:
<!DOCTYPE html>
<html>
<head>
<title>CANVAS</title>
</head>
<body>
<canvas id="smallImage" width="600" height="600"></canvas>
<script>
var imgid = document.getElementById('smallImage');
var ctx = imgid.getContext('2d');
var img = new Image();
var immmagine = "flowers.jpg";
img.src = immmagine;
ctx.drawImage(img,0,0);
</script>
</body>
</html>
You need to use the onload event.
img.onload = function() {
ctx.drawImage(img,0,0);
}
You need to listen the onload event on your image :
var imgid = document.getElementById('smallImage');
var ctx = imgid.getContext('2d');
var img = new Image();
var immmagine = "flowers.jpg";
img.src = immmagine;
img.onload = function ()
{
ctx.drawImage(img,0,0);
}