I am trying to fill the rectangle that i have drawn onto a canvas using Javascript. However when i try with the below code my rectangle doesn't even render at all with no error messages i am unsure what i have done wrong. suggestions?
ctx.beginPath();
ctx.rect(150, 0, 3, 75);
var img = new Image();
img.src = window.location.host + "/wp-content/plugins/productdesigner/assets/Cords/T-911 Neon Orange.jpg";
img.onload = function() {
var pattern = ctx.createPattern(this,"repeat");
ctx.fillStyle = pattern;
ctx.fill();
};
ctx.closePath();
Related
I'm using the solution from: How to check if a canvas is blank? but it's not working. My blank canvas URL does not match the newly created canvas URL and I cannot figure out why. They are the same dimensions and everything but their .toDataURL return different things so there is no way for me to tell if it has been drawn in. Below is an example of what happens when I do .toDataURL on my blank canvas and .toDataURL on the newly created canvas, as you can see they differ as you continue along.
data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAA0sAAACUCAYAAABCxLIRAAAKfUlEQVR4Xu3ZIRKAQAwEQfj/ow9NgRi/jY5J58wU9znnXD4CBAgQIECAAAECBAgQeAncYsmLIECAAAECBAgQIECAwFdALHkVBAgQIECAAAECBAgQ+BEQS54FAQIECBAgQIAAAQIExJI3QIAAAQIECBAgQIAAgSbgz1JzMkWAAAECBAgQIECAwJiAWBo7uHUJECBAgAABAgQIEGgCYqk5mSJAgAABAgQIECBAYExALI0d3LoECBAgQIAAAQIECDQBsdScTBEgQIAAAQIECBAgMCYglsYObl0CBAgQIECAAAECBJqAWGpOpggQIECAAAECBAgQGBMQS2MHty4BAgQIECBAgAABAk1ALDUnUwQIECBAgAABAgQIjAmIpbGDW5cAAQIECBAgQIAAgSYglpqTKQIECBAgQIAAAQIExgTE0tjBrUuAAAECBAgQIECAQBMQS83JFAECBAgQIECAAAECYwJiaezg1iVAgAABAgQIECBAoAmIpeZkigABAgQIECBAgACBMQGxNHZw6xIgQIAAAQIECBAg0ATEUnMyRYAAAQIECBAgQIDAmIBYGju4dQkQIECAAAECBAgQaAJiqTmZIkCAAAECBAgQIEBgTEAsjR3cugQIECBAgAABAgQINAGx1JxMESBAgAABAgQIECAwJiCWxg5uXQIECBAgQIAAAQIEmoBYak6mCBAgQIAAAQIECBAYExBLYwe3LgECBAgQIECAAAECTUAsNSdTBAgQIECAAAECBAiMCYilsYNblwABAgQIECBAgACBJiCWmpMpAgQIECBAgAABAgTGBMTS2MGtS4AAAQIECBAgQIBAExBLzckUAQIECBAgQIAAAQJjAmJp7ODWJUCAAAECBAgQIECgCYil5mSKAAECBAgQIECAAIExAbE0dnDrEiBAgAABAgQIECDQBMRSczJFgAABAgQIECBAgMCYgFgaO7h1CRAgQIAAAQIECBBoAmKpOZkiQIAAAQIECBAgQGBMQCyNHdy6BAgQIECAAAECBAg0AbHUnEwRIECAAAECBAgQIDAmIJbGDm5dAgQIECBAgAABAgSagFhqTqYIECBAgAABAgQIEBgTEEtjB7cuAQIECBAgQIAAAQJNQCw1J1MECBAgQIAAAQIECIwJiKWxg1uXAAECBAgQIECAAIEmIJaakykCBAgQIECAAAECBMYExNLYwa1LgAABAgQIECBAgEATEEvNyRQBAgQIECBAgAABAmMCYmns4NYlQIAAAQIECBAgQKAJiKXmZIoAAQIECBAgQIAAgTEBsTR2cOsSIECAAAECBAgQINAExFJzMkWAAAECBAgQIECAwJiAWBo7uHUJECBAgAABAgQIEGgCYqk5mSJAgAABAgQIECBAYExALI0d3LoECBAgQIAAAQIECDQBsdScTBEgQIAAAQIECBAgMCYglsYObl0CBAgQIECAAAECBJqAWGpOpggQIECAAAECBAgQGBMQS2MHty4BAgQIECBAgAABAk1ALDUnUwQIECBAgAABAgQIjAmIpbGDW5cAAQIECBAgQIAAgSYglpqTKQIECBAgQIAAAQIExgTE0tjBrUuAAAECBAgQIECAQBMQS83JFAECBAgQIECAAAECYwJiaezg1iVAgAABAgQIECBAoAmIpeZkigABAgQIECBAgACBMQGxNHZw6xIgQIAAAQIECBAg0ATEUnMyRYAAAQIECBAgQIDAmIBYGju4dQkQIECAAAECBAgQaAJiqTmZIkCAAAECBAgQIEBgTEAsjR3cugQIECBAgAABAgQINAGx1JxMESBAgAABAgQIECAwJiCWxg5uXQIECBAgQIAAAQIEmoBYak6mCBAgQIAAAQIECBAYExBLYwe3LgECBAgQIECAAAECTUAsNSdTBAgQIECAAAECBAiMCYilsYNblwABAgQIECBAgACBJiCWmpMpAgQIECBAgAABAgTGBMTS2MGtS4AAAQIECBAgQIBAExBLzckUAQIECBAgQIAAAQJjAmJp7ODWJUCAAAECBAgQIECgCYil5mSKAAECBAgQIECAAIExAbE0dnDrEiBAgAABAgQIECDQBMRSczJFgAABAgQIECBAgMCYgFgaO7h1CRAgQIAAAQIECBBoAmKpOZkiQIAAAQIECBAgQGBMQCyNHdy6BAgQIECAAAECBAg0AbHUnEwRIECAAAECBAgQIDAmIJbGDm5dAgQIECBAgAABAgSagFhqTqYIECBAgAABAgQIEBgTEEtjB7cuAQIECBAgQIAAAQJNQCw1J1MECBAgQIAAAQIECIwJiKWxg1uXAAECBAgQIECAAIEmIJaakykCBAgQIECAAAECBMYExNLYwa1LgAABAgQIECBAgEATEEvNyRQBAgQIECBAgAABAmMCYmns4NYlQIAAAQIECBAgQKAJiKXmZIoAAQIECBAgQIAAgTEBsTR2cOsSIECAAAECBAgQINAExFJzMkWAAAECBAgQIECAwJiAWBo7uHUJECBAgAABAgQIEGgCYqk5mSJAgAABAgQIECBAYExALI0d3LoECBAgQIAAAQIECDQBsdScTBEgQIAAAQIECBAgMCYglsYObl0CBAgQIECAAAECBJqAWGpOpggQIECAAAECBAgQGBMQS2MHty4BAgQIECBAgAABAk1ALDUnUwQIECBAgAABAgQIjAmIpbGDW5cAAQIECBAgQIAAgSYglpqTKQIECBAgQIAAAQIExgTE0tjBrUuAAAECBAgQIECAQBMQS83JFAECBAgQIECAAAECYwJiaezg1iVAgAABAgQIECBAoAmIpeZkigABAgQIECBAgACBMQGxNHZw6xIgQIAAAQIECBAg0ATEUnMyRYAAAQIECBAgQIDAmIBYGju4dQkQIECAAAECBAgQaAJiqTmZIkCAAAECBAgQIEBgTEAsjR3cugQIECBAgAABAgQINAGx1JxMESBAgAABAgQIECAwJiCWxg5uXQIECBAgQIAAAQIEmoBYak6mCBAgQIAAAQIECBAYExBLYwe3LgECBAgQIECAAAECTUAsNSdTBAgQIECAAAECBAiMCYilsYNblwABAgQIECBAgACBJiCWmpMpAgQIECBAgAABAgTGBMTS2MGtS4AAAQIECBAgQIBAExBLzckUAQIECBAgQIAAAQJjAmJp7ODWJUCAAAECBAgQIECgCYil5mSKAAECBAgQIECAAIExAbE0dnDrEiBAgAABAgQIECDQBMRSczJFgAABAgQIECBAgMCYgFgaO7h1CRAgQIAAAQIECBBoAmKpOZkiQIAAAQIECBAgQGBMQCyNHdy6BAgQIECAAAECBAg0AbHUnEwRIECAAAECBAgQIDAmIJbGDm5dAgQIECBAgAABAgSagFhqTqYIECBAgAABAgQIEBgTEEtjB7cuAQIECBAgQIAAAQJNQCw1J1MECBAgQIAAAQIECIwJiKWxg1uXAAECBAgQIECAAIEmIJaakykCBAgQIECAAAECBMYExNLYwa1LgAABAgQIECBAgEATEEvNyRQBAgQIECBAgAABAmMCYmns4NYlQIAAAQIECBAgQKAJiKXmZIoAAQIECBAgQIAAgTGBB7R+TmNlhJuwAAAAAElFTkSuQmCC
data:image/png;base64,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
For reference here is the function:
function isCanvasBlank(canvas) {
var blank = document.createElement('canvas');
blank.width = canvas.width;
blank.height = canvas.height;
return canvas.toDataURL() == blank.toDataURL();
}
the resulting images you have are different. The first one has a white background and the other is transparent.
This is causing the difference.
this is a quick way to fill the new canvas.
function isCanvasBlank(canvas) {
var blank = document.createElement('canvas');
blank.width = canvas.width;
blank.height = canvas.height;
var ctx = blank.getContext("2d");
ctx.fillStyle = "#FFFFFF";
ctx.fillRect(0, 0, blank .width, blank .height);
return canvas.toDataURL() == blank.toDataURL();
}
or use same function as the fiddle. blank.getContext('2d').clearRect(0, 0, canvas.width, canvas.height);
function isCanvasBlank(canvas) {
var blank = document.createElement('canvas');
blank.width = canvas.width;
blank.height = canvas.height;
blank.getContext('2d').clearRect(0, 0, canvas.width, canvas.height);
return canvas.toDataURL() == blank.toDataURL();
}
I am working on a dynamic web map with HTML5 and canvas.
I loaded the map in PNG format, but whenever I try to draw on it, it draws behind the map like this:
I need it to draw over the white squares.
This is my code:
window.onload = function() {
var canvas = document.getElementById('canvas1');
var ctx = canvas.getContext('2d');
var img = new Image();
img.onload = function() {
ctx.drawImage(img, 0, 0);
}
img.src = "img/plano.png"; //transparent png
ctx.fillRect(1039, 150, 50, 50);
}
Thanks in advance!
The fillRect needs to happen after the image has loaded. The image loads asynchronously so the only safe place for this to happen is after the drawImage...
img.onload = function() {
ctx.drawImage(img, 0, 0);
ctx.fillRect(200,200,50,50); // Draw rect after image
}
So I am creating a cordova app where I take a photo from the iphone library, draw it to canvas and add another image to it in order to save it as one photo. So far the photo I draw from the iphone photo library gets drawn without problems to the canvas, however the second image doesn't.
When I load the second image, it first gets added to a div with absolute positioning in order to move it to wherever I want. After that I get the actual image it's source and it's positions and try to draw it to canvas. The drawing of the second image happens when I call a method that also performs the canvas2ImagePlugin it's functions. In the end only the first photo without the second image gets saved.
The draw image to canvas function:
function drawImage(image_source, dx, dy)
{
var canvas = document.getElementById('Photo');
var image = new Image();
image.src = image_source;
image.onload = function() {
c=canvas.getContext("2d");
c.canvas.width = window.innerWidth;
c.canvas.height = window.innerHeight;
c.drawImage(image,dx,dy, window.innerWidth, window.innerHeight);
}
}
The method for drawing the second image and saving it:
function saveImage()
{
var img = $('.ObjectImage').attr('src', $('img:first').attr('src'));
var imagePosition = $('.ObjectImage').find('img:first').position();
drawImage(img, imgPosition.left, imgPosition.top);
window.canvas2ImagePlugin.saveImageDataToLibrary(
function(msg){
console.log(msg);
},
function(err){
console.log(err);
},
document.getElementById('Photo')
);
alert("Image saved");
}
The window.innerWidth, window.innerHeight on the canvas is done to get the canvas in full screen of the parent div.
EDIT to the comment:
function drawImage(image_source, dx, dy)
{
var canvas = document.getElementById('Photo');
var image = new Image();
image.onload = function() {
c=canvas.getContext("2d");
c.canvas.width = window.innerWidth;
c.canvas.height = window.innerHeight;
c.drawImage(image,dx,dy, window.innerWidth, window.innerHeight);
}
image.src = image_source;
}
Still not working
The drawImage function works asynchronously, it starts loading an image and exits immediately. Then, when the image loads, the canvas is updated. If you run something like:
drawImage('test.jpg',0,0);
drawImage('test2.jpg',0,0);
you will get both images updating the canvas at approximately the same time and only one will appear.
Also, what wolfhammer said is correct. If you set the size of the canvas, you clear it, so drawing one image after the other, even if they are smaller sizes and should both appear, will only show the last one. Check this link on how to solve it: Preventing Canvas Clear when Resizing Window
Further more, you are drawing all images with the width and height of the window, which doesn't make sense. Probably you want to use the width and height of the image (so this.width instead of window.innerWidth)
When you set the width and height of the canvas the data on "Photo" is cleared. I've provide a resize function if resizing is really needed.
function drawImage(image_source, dx, dy)
{
var canvas = document.getElementById('Photo');
var image = new Image();
image.src = image_source;
image.onload = function() {
c=canvas.getContext("2d");
//c.canvas.width = window.innerWidth;
//c.canvas.height = window.innerHeight;
c.drawImage(image,dx,dy, window.innerWidth, window.innerHeight);
}
}
var can = document.getElementById('can');
var ctx = can.getContext('2d');
ctx.fillStyle = "red";
ctx.beginPath();
ctx.moveTo(20, 90);
ctx.lineTo(50, 10);
ctx.lineTo(80, 90);
ctx.lineTo(10, 40);
ctx.lineTo(90, 40);
ctx.lineTo(20, 90);
ctx.fill();
var btn = document.getElementById('btnResize');
btn.addEventListener('click', function() {
resize(can, can.width * 2, can.height * 2);
});
function resize(can, w, h) {
var ctx = can.getContext('2d');
// copy
var can2 = document.createElement('canvas');
var ctx2 = can2.getContext('2d');
can2.width = can.width;
can2.height = can.height;
ctx2.drawImage(can, 0, 0);
// resize
can.width = w;
can.height = h;
ctx.drawImage(can2, 0, 0, can2.width, can2.height, 0, 0, w, h);
}
#can {
border:1px solid red;
}
<button id='btnResize'>Size x 2</button><br/>
<canvas id="can" width="100" height="100"></canvas>
i just want to make a page where u can type a text and add it on selected image and save that as new image.
I tried to do it in few ways, but without luck.
<body>
<canvas id = "idCanvas" width = "576" height = "577"> </canvas>
<img id="canvasImg" width = "576" height = "577"></img>
<script>
window.onload = function(){
var canvas = document.getElementById('idCanvas');
var context = canvas.getContext('2d');
var imageObj = new Image();
var dataURL = canvas.toDataURL();
imageObj.onload = function() {
context.drawImage(imageObj, 0, 0, 576, 577);
context.font = "20px Calibri";
context.fillText("My TEXT!", 50, 200);
document.getElementById('canvasImg').src = toDataURL();
window.alert(dataURL);
};
imageObj.src = "image.png";
};
</script>
When i use toDataURL() in img src, the image won't be displayed, it only works if i'm not using drawImage in canvas.
Ok so yes it will not work for security reason, but there is a solution.
See here a working demo: FIDDLE
draw();
function draw() {
var canvas = document.getElementById('idCanvas');
var context = canvas.getContext('2d');
var imageObj = new Image();
imageObj.onload = function() {
context.drawImage(imageObj, 0, 0);
context.font = "40px Calibri";
context.fillStyle = "red";
context.fillText("My TEXT!", 50, 300);
var canvas = document.getElementById('idCanvas');
var dataURL = canvas.toDataURL();
alert(dataURL);
}
imageObj.setAttribute('crossOrigin', 'anonymous');
imageObj.src = "https://loremflickr.com/400/200";
};
First of all, Should it be canvas.toDataURL() ?
Here is a similar example with getting contents into image element http://www.html5canvastutorials.com/advanced/html5-canvas-save-drawing-as-an-image/
Also I was getting the following error when image is loaded from another hostname:
Uncaught SecurityError: Failed to execute 'toDataURL' on
'HTMLCanvasElement': Tainted canvases may not be exported.
When image is not added to canvas it works fine, so issue could be related to CORS HTTP headers not added with image. Try removing
context.drawImage(imageObj, 0, 0, 576, 577);
to see that it works without image
Here is a demo based on code in question.
http://jsbin.com/logikuwefo/1/edit
here is the jsfiddle
i have this as my source canvas
HTML
<h1>Source Canvas</h1>
<canvas id="source" width=436 height=567></canvas>
<h1>Destination Canvas</h1>
<canvas id="destination" width=436 height=567></canvas>
javascript
var sourceImage, ctx, sourceCanvas, destinationCanvas;
//get the canvases
sourceCanvas = document.getElementById('source');
destinationCanvas = document.getElementById('destination');
//draw the source image to the source canvas
ctx = sourceCanvas.getContext('2d');
function start() {
ctx.drawImage(img1, 0, 0);
ctx.globalCompositeOperation = "source-atop";
var pattern = ctx.createPattern(img, 'repeat');
ctx.rect(0, 0, sourceCanvas.width, sourceCanvas.height);
ctx.fillStyle = pattern;
ctx.fill();
ctx.globalAlpha = .10;
ctx.drawImage(img1, 0, 0);
ctx.drawImage(img1, 0, 0);
ctx.drawImage(img1, 0, 0);
//ctx.globalAlpha = 1;
}
var img1 = new Image();
var img = new Image();
img.onload = function () {
img1.onload = function () {
start();
}
img1.src = "https://dl.dropboxusercontent.com/u/139992952/stackoverflow/4jiSz1.png";
}
img.src = "https://dl.dropboxusercontent.com/u/139992952/stackoverflow/BooMu1.png";
i want to to show what is in source canvas in my destination canvas.
i tired
var image, destinationCtx;
//create the image
image = new Image();
//get the base64 data
image.src = sourceCanvas.toDataURL('image/png');
//get the destination context
destinationCtx = destinationCanvas.getContext('2d');
//copy the data
destinationCtx.drawImage(image, 0, 0);
//done
but having no luck. am i missing something?
Copy via imageData,Copy via Base64 data,Copy via direct draw any method will do my job.
when i try with
http://jsperf.com/copying-a-canvas-element
it copies but when i put my source canvas writer it does not work ? am i missing something?
You can directly copy one canvas over other. Like this...
var destinationCtx;
//get the destination context
destinationCtx = destinationCanvas.getContext('2d');
//copy the data
destinationCtx.drawImage(sourceCanvas, 0, 0);
You can use getImageData from the source canvas and putImageData to the destination canvas.This is the fastest one compare to other ways.
var sourceCtx, destinationCtx, imageData;
sourceCtx = sourceCanvas.getContext('2d');
destinationCtx = destinationCanvas.getContext('2d');
imageData = sourceCtx.getImageData(0, 0, sourceCanvas.width - 1, sourceCanvas.height - 1);
destinationCtx.putImageData(imageData, 0, 0);
source:/ https://jsperf.com/copying-a-canvas-element