Develop Reference

Unable to load an Image into Canvas and get base64 encoding for that image

I am trying to generate a PDF from HTML using jspdf plugin. I am stuck with loading Images into PDF. There is a function addImage() in plugin which takes base64 encoding of an image, but converting an image to base64 is not working.
I have used below two ways
//Create canvas, draw image in context and get the data url
imgToDataURL = function (img, outputFormat){
var canvas = document.createElement('canvas');
canvas.width = 20;
canvas.height = 20;
var c = canvas.getContext('2d');
c.height = img.height;
c.width=img.width;
c.drawImage(img, 0, 0);
c.save();
var dataurl = canvas.toDataURL(outputFormat);
return dataurl;
}
var img = new Image();
img.crossOrigin = 'Anonymous';
img.src = "image path"
img.height= 60;
img.width=60;
var dataURL = this.imgToDataURL(img,"image/jpeg");
renderer.pdf.addImage(dataURL, 'png',x+padding,y + this.internal.getLineHeight(),imageWidth,imageHeight);
This is printing wrong dataURL I am getting a white image. If I hard code the base64 code i.e return a hardcoded dataURL then addImage works fine. So the issue is with canvas.toDataURL which is giving me wrong output
this is the 2nd way
convertImgToBase64URL = function (url, callback, outputFormat){
var img = new Image();
img.crossOrigin = 'Anonymous';
img.onload = function(){
var canvas = document.createElement('CANVAS'),
ctx = canvas.getContext('2d'), dataURL;
canvas.height = this.height;
canvas.width = this.width;
ctx.drawImage(this, 0, 0);
dataURL = canvas.toDataURL(outputFormat);
callback(dataURL);
canvas = null;
};
img.src = url;
}
this.convertImgToBase64URL("Image Path",function(base64){
renderer.pdf.addImage(base64, 'PNG', 20, 20,48,48);
})
I have run this inside a javascript and the onload function is not even running I am not sure what is my mistake is.
Please suggest me what mistake I am doing in either way

In the first you missed assigning an onload function to your image. For that reason, the moment you try to create the dataURL, the image might not be loaded yet, ergo, the blank image. You could try changing the last few lines to this:
...
img.width=60;
img.onload = function () {
var dataURL = this.imgToDataURL(img,"image/jpeg");
renderer.pdf.addImage(dataURL, 'png',x+padding,y + this.internal.getLineHeight(),imageWidth,imageHeight);
}
img.src = "image path";
As for the second one, there seems to be a problem with the convertImgToBase64URL() which accepts 3 parameters, but you are passing 2. In you example, outputFormat parameter is undefined.

How to resize the image before base64 conversion

In my sencha based application i want to convert the image into base64,Before that i want to resize the original one.Here the code which i have used to convert base64
function getBase64FromImageUrl(URL)
{
var img = new Image();
img.style.width = '5%',
img.style.height = '5%',
img.src = URL;
img.onload = function ()
{
var canvas = document.createElement("canvas");
canvas.width =this.width;
canvas.height =this.height;
var ctx = canvas.getContext("2d");
ctx.drawImage(this, 10, 10);
var dataURL = canvas.toDataURL("image/jpg");
if(App.gvars.userpic=='1')
{
cdd=dataURL.replace(/^data:image\/(png|jpg);base64,/, "");
}
if(App.gvars.userpic=='2')
{
c=dataURL.replace(/^data:image\/(png|jpg);base64,/, "");
}
}
}
How to resize or redimension the image before conversion?I have tried with changing img.style.width and hieght but there is no change at all.Please help me

Per devnull69's suggestion, simply use drawImage() to resize the image when you add it into the canvas.
See the API at either W3Schools or MSDN.
You can even play with the values in a live-coding example at Html5CanvasTutorials

Loading Image into document.body Background

I'm attempting to pull an image (in this case, /camera/frame, which is a known-good JPG), and load it as the background of my document.body.
Here's my code thus far:
var backgroundImage = new Image();
backgroundImage.onload = function ()
{
console.log("onload");
document.body.style.backgroundImage = this.src;
};
backgroundImage.src = 'camera/frame';
"onload" prints as expected, and this.src prints out the full URL to /camera/frame, however document.body.style.backgroundImage remains "".

I believe you may be missing two things.
var path = 'path/to/image.jpg';
document.body.style.background='url('+path+')';

Canvas 2D to the rescue!
var backgroundImage = new Image();
backgroundImage.onload = function ()
{
var canvas = document.getElementById('canvas');
canvas.width = this.width;
canvas.height = this.height;
var canvasContext = canvas.getContext('2d');
canvasContext.drawImage(this, 0, 0, this.width, this.height);
};
backgroundImage.src = 'camera/frame';
backgroundImage.width = $(window).width();
backgroundImage.height = $(window).height();
Loads the image in the background, then draws it into the canvas seamlessly!

jQuery: how to get the dimensions of a external image?

Looking for a way to get the dimensions (width and height) of an external image. I have used prop() and attr(), but they don't return any values. Just an error.
Example:
some link

jQuery
var path = 'https://source.unsplash.com/random/600x300/?montreal';
$("<img/>").attr('src', path).load(function() {
console.log(this.width, this.height);
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.2.4/jquery.min.js"></script>
Vanilla Javascript
var path = 'https://source.unsplash.com/random/600x300/?montreal';
var img = new Image();
img.src = path;
img.addEventListener('load', function() {
console.log(this.width, this.height);
});

Looks like none has provided a working vanilla js answer.
var img = document.createElement('img')
img.src = 'http://domain.com/img.png'
img.onload = function() {
console.log( this.width )
console.log( this.height )
}
Here is a jsfiddle: http://jsfiddle.net/Ralt/VMfVZ/

This isn't technically jQuery but I would go down the route of:
var image = new Image(), width, height;
image.src = 'http://whereyourimage.is/heresmyimage.jpg';
width = image.width;
height = image.height;
You can then access those values using width and height, for example alert('My image is ' + width + ' pixels accross.');

How to display image with JavaScript?

I am trying to display image, through JavaScript, but i can't figure out how to do that. I have following
function image(a,b,c)
{
this.link=a;
this.alt=b;
this.thumb=c;
}
function show_image()
{
document.write("img src="+this.link+">");
}
image1=new image("img/img1.jpg","dsfdsfdsfds","thumb/img3");
in HTML
<p><input type="button" value="Vytvor" onclick="show_image()" > </p>
I can't figure out where should I put something like image1.show_image();.
HTML? Or somewhere else...

You could make use of the Javascript DOM API. In particular, look at the createElement() method.
You could create a re-usable function that will create an image like so...
function show_image(src, width, height, alt) {
var img = document.createElement("img");
img.src = src;
img.width = width;
img.height = height;
img.alt = alt;
// This next line will just add it to the <body> tag
document.body.appendChild(img);
}
Then you could use it like this...
<button onclick=
"show_image('http://google.com/images/logo.gif',
276,
110,
'Google Logo');">Add Google Logo</button>
See a working example on jsFiddle: http://jsfiddle.net/Bc6Et/

Thank you... I made small modifications/simplifications. Works as intended.
HTML:
Add Image
Javascript:
function addLogo() {
var src = "https://i.gifer.com/origin/93/935d72c7bc35828ea93b5898691f28fd_w200.gif";
show_image(src, 124,124, "My Image");
}
function show_image(src, width, height, alt) {
var img = document.createElement("img");
img.src = src;
img.width = width;
img.height = height;
img.alt = alt;
document.body.appendChild(img);
}