I retrieve a user from the database who has profile picture. This picture is base64 and drawImage to the canvas. but it failed to draw.
Here's my code:
var userId = {'userId' : 1};
$scope.user = UserProfileService.getUserProfile.query(userId, function() {
var canvas = document.getElementById("mycanvasweb");
var ctx = canvas.getContext("2d");
var image = new Image();
image.onload = function() {
ctx.drawImage(this, 0, 0);
};
image.src = $scope.user.profilePic;
});
Please help.
Related
I'm trying to create a smaller thumbnail of an image on a canvas.
The thumbnail size I'd like is 200 x 200
According to the documentation it should be as easy as drawImage(img, 0, 0, 200, 200) but I get the same results here is my code:
_canvas = document.createElement('canvas'),
ctx = _canvas.getContext("2d"),
img = new Image();
img.onload = function() {
ctx.drawImage(this, 0, 0, 1200, 600);
var dataURL = _canvas.toDataURL();
// The above creates the first image
//Then while I'm still in the load method I attempt to save another size:
ctx.drawImage(this,0,0,300,300);
var dataThumbURL = _canvas.toDataURL();
}
I save both dataURL and dataThumbURL to the server and both images are the same size.
My assumption is ctx.drawImage could be repeated with just a different size. Any idea how I can achieve this?
The width and height parameters of the drawImage() method do not alter the dimensions of the canvas you draw onto. So if your source image is bigger than the canvas it will simply be cropped.
To have snapshots of different sizes, you need to change the dimensions of the canvas to the desired size prior calling drawImage().
Here's an example:
let image = new Image();
let _canvas = document.createElement('canvas');
let ctx = _canvas.getContext("2d");
image.crossOrigin = "";
image.onload = function() {
let img, dataURL;
_canvas.width = 200;
_canvas.height = 150;
ctx.drawImage(this, 0, 0, _canvas.width, _canvas.height);
dataURL = _canvas.toDataURL();
img = new Image();
document.body.appendChild(img);
img.src = dataURL;
_canvas.width = 40;
_canvas.height = 30;
ctx.drawImage(this, 0, 0, _canvas.width, _canvas.height);
dataURL = _canvas.toDataURL();
img = new Image();
document.body.appendChild(img);
img.src = dataURL;
}
image.src = "https://api.codetabs.com/v1/proxy?quest=https://picsum.photos/id/237/200/300";
I have to work with pdfmake to build a pdf preview within my laravel application. I am a javascript noob and going nuts to generate the dataURI for an image in b. Hope you can help me out.
How can I get that generated base64 into my docdefinition?
function convertImageToDataURL(src, callback, outputFormat) {
// Create an Image object
var img = new Image();
// Add CORS approval to prevent a tainted canvas
img.crossOrigin = 'Anonymous';
img.onload = function() {
var canvas = document.createElement('CANVAS');
var ctx = canvas.getContext('2d');
var dataURL;
canvas.height = this.naturalHeight;
canvas.width = this.naturalWidth;
ctx.drawImage(this, 0, 0);
dataURL = canvas.toDataURL(outputFormat);
callback(dataURL);
// Mark the canvas to be ready for garbage
// collection
canvas = null;
};
img.src = src;
// make sure the load event fires for cached images too
if (img.complete || img.complete === undefined) {
// Flush cache
img.src = 'data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw==';
// Try again
img.src = src;
}
}
convertImageToDataURL(
'{{asset('storage/'.$report->author->enterprises->first()->logo_image)}}',
function(dataUrl) {
// console.log('RESULT:', dataUrl);
// Put dataUrl into DocDefinition here!?!?
// return dataUrl is undefined
}
);`
Okay. As I said: I am a javascript noob. So I changed the script to this one:
function convertImageToDataURL(imgSrc) {
img = new Image();
img.src = imgSrc;
img.crossOrigin = "Anonymous";
var canvas = document.createElement("canvas");
canvas.width = img.naturalWidth;
canvas.height = img.naturalHeight;
var ctx = canvas.getContext("2d");
ctx.drawImage(img, 0, 0);
var dataURL = canvas.toDataURL("image/jpg");
canvas = null;
return dataURL;
}
It might not be beautyful nor elegant, but it works for me.
I'm trying to draw an existing image onto a canvas and encode it via base64. Here is my code:
var canvas = document.createElement("canvas");
canvas.id = "MyCanvas";
document.getElementById("Table1").appendChild(canvas);
var myCanvas = document.getElementById("MyCanvas");
var myCanvasContext = myCanvas.getContext("2d");
myCanvas.width = 135;
myCanvas.height = 170;
var img = new Image();
img.onload = function(){
myCanvasContext.drawImage(img,0,0);
}
img.src = "https://example.com/asd.png";
var toURL = myCanvas.toDataURL();
console.log(toURL);
It draws the image to the canvas, but the toURL is an empty image base64 code with 135x170 size. I've tried to decode it, but it always shows a blank image.
I can't find what is the problem with it.
The problem is that myCanvas.toDataURL(); is called before the image is actually loaded. For this you'd need to move it inside the onload-callback, like:
var img = new Image();
img.onload = function(){
myCanvasContext.drawImage(img,0,0);
// ...moved here
var toURL = myCanvas.toDataURL();
console.log(toURL);
}
img.src = "https://example.com/asd.png";
The following is a simplified example:
const canvas = document.createElement('canvas');
const ctx = canvas.getContext('2d');
const img = new Image();
img.crossOrigin = "";
img.src = 'https://www.gravatar.com/avatar/8939f42cb6c31e31e570ea8f07fe9757?s=32&d=identicon&r=PG';
img.onload = () => {
canvas.width = img.naturalWidth;
canvas.height = img.naturalHeight;
ctx.drawImage(img, 0, 0);
console.log(canvas.toDataURL());
};
document.body.appendChild(canvas); // append the canvas ...
document.body.appendChild(img); // ... and img for demo purposes only
var canvas = document.createElement("canvas");
canvas.id = "MyCanvas";
document.getElementById("Table1").appendChild(canvas);
var myCanvas = document.getElementById("MyCanvas");
var myCanvasContext = myCanvas.getContext("2d");
myCanvas.width = 500;
myCanvas.height = 500;
var img = new Image();
img.onload = function(){
myCanvasContext.drawImage(img,0,0);
}
img.src = "http://underthebridge.co.uk/wp-content/uploads/2014/03/Example-main-image1.jpg";
var toURL = myCanvas.toDataURL();
console.log(toURL);
var img2 = document.createElement("img");
img2.id = "MyImg";
img2.src = toURL;
document.getElementById("Table1").appendChild(img2);
<div id='Table1'> </div>
You can't put an base64 inside a canvas but only in a tag img.
I have a canvas and I want to convert it and show in a tag. I know we can convert canvas to image by using toDataURL() and toBlob() but both method give me base64 data which is not a image.
$("#upload_feedback_btn").on("click", function() {
let feedbackSrc = document.getElementById("capture").toDataURL('image/png', 1.0);
$("#feedback_canvas_image").append("<img id='upload_canvas_img' src="+feedbackSrc+">");
});
var can = document.getElementById('canvas1');
var ctx = can.getContext('2d');
ctx.fillRect(50,50,50,50);
var img = new Image();
img.src = can.toDataURL();
document.body.appendChild(img);
http://jsfiddle.net/simonsarris/vgmFN/
Use this, pure javascript:
var canvas = document.getElementById('canvas'),
context = canvas.getContext('2d');
make_base();
function make_base()
{
base_image = new Image();
base_image.src = 'img/base.png';
base_image.onload = function(){
context.drawImage(base_image, 100, 100);
}
}
I want to ask you what's wrong with my code below :
var myCanvas = document.getElementById('myCanvas');
var ctx = myCanvas.getContext('2d');
var image = new Image();
image.onload = onLoad;
image.src = './PS_Countdown.jpeg';
ctx.drawImage(image, 25, 25);
function onLoad() {
console.log('Image loaded');
}