I am trying to paint an image on a canvas before I get its dataURL(), but the data returned is like empty.
When I check it in the console, I see there is a lot of A in the string : ("data:image/png;base64,iVBO..some random chars... bQhfoAAAAAAAAAA... a lot of A ...AAAASUVORK5CYII=")
When I try to append the canvas to the document, nothing is drawn either and I don't have any error thrown in the console.
What is the problem here ?
Here is my code :
var img = new Image();
img.src = "http://somerandomWebsite/picture.png";
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var context = canvas.getContext('2d');
context.drawImage(img, 0,0); // this doesn't seem to work
var dataURL = canvas.toDataURL(); // this will give me a lot of "A"
doSomething(dataURL);
Also, when doing a quick refresh, the image gets drawn correctly onto the canvas but I've got an error message in the console and dataURL is empty.
The message in Firefox is : "SecurityError: The operation is insecure.",
in Chrome it is "Uncaught SecurityError: Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported.",
and on IE I just get "SecurityError".
What does it mean ?
You have to wait that your image has loaded before you can paint it on the canvas.
To do so, simply use the load event handler of your <img> element :
// create a new image
var img = new Image();
// declare a function to call once the image has loaded
img.onload = function(){
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var context = canvas.getContext('2d');
context.drawImage(img, 0,0);
var dataURL = canvas.toDataURL();
// now you can do something with the dataURL
doSomething(dataURL);
}
// now set the image's src
img.src = "http://somerandomWebsite/picture.png";
Also, for the canvas' context.toDataURL() and context.getImageData to work properly, you have to get your image resource in a cross-origin compliant way, otherwise the canvas is "tainted" which means that any method to get pixels data will be blocked.
If your image comes from the same server, no problem.
If your image is served from an external server, be sure that it allows yours in its cross-origin headers and set the img.crossOrigin to "use-credentials".
If the server does allow anonymous requests, you can set the img.crossOrigin to "anonymous".
Nota Bene : CORS header is sent by the server, the cross-origin attribute will only let it know that you want to use CORS to get the image data, in no way you can circumvent it if the server is not set properly.
Also some UserAgents (IE & Safari) still haven't implemented this attribute.
Edge Case : If some of your images are from your server and some are from a CORS compliant one, then you may want to use the onerror event handler which should fire if you set the cross-origin attribute to "anonymous" on a non CORS server.
function corsError(){
this.crossOrigin='';
this.src='';
this.removeEventListener('error', corsError, false);
}
img.addEventListener('error', corsError, false);
Related
I am trying to paint an image on a canvas before I get its dataURL(), but the data returned is like empty.
When I check it in the console, I see there is a lot of A in the string : ("data:image/png;base64,iVBO..some random chars... bQhfoAAAAAAAAAA... a lot of A ...AAAASUVORK5CYII=")
When I try to append the canvas to the document, nothing is drawn either and I don't have any error thrown in the console.
What is the problem here ?
Here is my code :
var img = new Image();
img.src = "http://somerandomWebsite/picture.png";
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var context = canvas.getContext('2d');
context.drawImage(img, 0,0); // this doesn't seem to work
var dataURL = canvas.toDataURL(); // this will give me a lot of "A"
doSomething(dataURL);
Also, when doing a quick refresh, the image gets drawn correctly onto the canvas but I've got an error message in the console and dataURL is empty.
The message in Firefox is : "SecurityError: The operation is insecure.",
in Chrome it is "Uncaught SecurityError: Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported.",
and on IE I just get "SecurityError".
What does it mean ?
You have to wait that your image has loaded before you can paint it on the canvas.
To do so, simply use the load event handler of your <img> element :
// create a new image
var img = new Image();
// declare a function to call once the image has loaded
img.onload = function(){
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var context = canvas.getContext('2d');
context.drawImage(img, 0,0);
var dataURL = canvas.toDataURL();
// now you can do something with the dataURL
doSomething(dataURL);
}
// now set the image's src
img.src = "http://somerandomWebsite/picture.png";
Also, for the canvas' context.toDataURL() and context.getImageData to work properly, you have to get your image resource in a cross-origin compliant way, otherwise the canvas is "tainted" which means that any method to get pixels data will be blocked.
If your image comes from the same server, no problem.
If your image is served from an external server, be sure that it allows yours in its cross-origin headers and set the img.crossOrigin to "use-credentials".
If the server does allow anonymous requests, you can set the img.crossOrigin to "anonymous".
Nota Bene : CORS header is sent by the server, the cross-origin attribute will only let it know that you want to use CORS to get the image data, in no way you can circumvent it if the server is not set properly.
Also some UserAgents (IE & Safari) still haven't implemented this attribute.
Edge Case : If some of your images are from your server and some are from a CORS compliant one, then you may want to use the onerror event handler which should fire if you set the cross-origin attribute to "anonymous" on a non CORS server.
function corsError(){
this.crossOrigin='';
this.src='';
this.removeEventListener('error', corsError, false);
}
img.addEventListener('error', corsError, false);
I run the following code on Internet Explorer, it throws a SecurityError on the line var canvasDataUrl = canvas.toDataURL();
var canvas = document.createElement('canvas');
var canvasContext = canvas.getContext('2d');
var img = new Image;
img.onload = function(){
canvasContext.drawImage(img,0,0);
var canvasDataUrl = canvas.toDataURL(); // error occurs here
console.log(canvasDataUrl);
};
img.src = 'https://via.placeholder.com/300x300';
What is the cause of that error, and how can I fix this ?
can you try crossOrigin
var img = new Image();
img.crossOrigin = "anonymous";
var canvas = document.createElement('canvas');
var canvasContext = canvas.getContext('2d');
var image = new Image();
image.crossOrigin = "anonymous";
image.onload = function (event) {
try {
canvasContext.drawImage(image, 0, 0, 200, 200);
console.log(canvas.toDataURL());
} catch (e) {
console.log(e);
}
};
image.src = "https://i.chzbgr.com/maxW500/1691290368/h07F7F378/"
The answer from #pc_coder is correct, and I want to provide some information about this error, you can see here https://developer.mozilla.org/en-US/docs/Web/HTML/CORS_enabled_image
Because the pixels in a canvas's bitmap can come from a variety of
sources, including images or videos retrieved from other hosts, it's
inevitable that security problems may arise.
As soon as you draw into a canvas any data that was loaded from
another origin without CORS approval, the canvas becomes tainted. A
tainted canvas is one which is no longer considered secure, and any
attempts to retrieve image data back from the canvas will cause an
exception to be thrown.
If the source of the foreign content is an HTML or SVG
element, attempting to retrieve the contents of the canvas isn't
allowed.
If the foreign content comes from an image obtained from either as
HTMLCanvasElement or ImageBitMap, and the image source doesn't meet
the same origin rules, attempts to read the canvas's contents are
blocked.
Calling any of the following on a tainted canvas will result in an error:
Calling getImageData() on the canvas's context
Calling toBlob() on the element itself
Calling toDataURL() on the canvas
Attempting any of these when the canvas is tainted will cause a SecurityError to be thrown. This protects users from having private data exposed by using images to pull information from remote web sites without permission.
I am trying to paint an image on a canvas before I get its dataURL(), but the data returned is like empty.
When I check it in the console, I see there is a lot of A in the string : ("data:image/png;base64,iVBO..some random chars... bQhfoAAAAAAAAAA... a lot of A ...AAAASUVORK5CYII=")
When I try to append the canvas to the document, nothing is drawn either and I don't have any error thrown in the console.
What is the problem here ?
Here is my code :
var img = new Image();
img.src = "http://somerandomWebsite/picture.png";
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var context = canvas.getContext('2d');
context.drawImage(img, 0,0); // this doesn't seem to work
var dataURL = canvas.toDataURL(); // this will give me a lot of "A"
doSomething(dataURL);
Also, when doing a quick refresh, the image gets drawn correctly onto the canvas but I've got an error message in the console and dataURL is empty.
The message in Firefox is : "SecurityError: The operation is insecure.",
in Chrome it is "Uncaught SecurityError: Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported.",
and on IE I just get "SecurityError".
What does it mean ?
You have to wait that your image has loaded before you can paint it on the canvas.
To do so, simply use the load event handler of your <img> element :
// create a new image
var img = new Image();
// declare a function to call once the image has loaded
img.onload = function(){
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var context = canvas.getContext('2d');
context.drawImage(img, 0,0);
var dataURL = canvas.toDataURL();
// now you can do something with the dataURL
doSomething(dataURL);
}
// now set the image's src
img.src = "http://somerandomWebsite/picture.png";
Also, for the canvas' context.toDataURL() and context.getImageData to work properly, you have to get your image resource in a cross-origin compliant way, otherwise the canvas is "tainted" which means that any method to get pixels data will be blocked.
If your image comes from the same server, no problem.
If your image is served from an external server, be sure that it allows yours in its cross-origin headers and set the img.crossOrigin to "use-credentials".
If the server does allow anonymous requests, you can set the img.crossOrigin to "anonymous".
Nota Bene : CORS header is sent by the server, the cross-origin attribute will only let it know that you want to use CORS to get the image data, in no way you can circumvent it if the server is not set properly.
Also some UserAgents (IE & Safari) still haven't implemented this attribute.
Edge Case : If some of your images are from your server and some are from a CORS compliant one, then you may want to use the onerror event handler which should fire if you set the cross-origin attribute to "anonymous" on a non CORS server.
function corsError(){
this.crossOrigin='';
this.src='';
this.removeEventListener('error', corsError, false);
}
img.addEventListener('error', corsError, false);
I am trying to paint an image on a canvas before I get its dataURL(), but the data returned is like empty.
When I check it in the console, I see there is a lot of A in the string : ("data:image/png;base64,iVBO..some random chars... bQhfoAAAAAAAAAA... a lot of A ...AAAASUVORK5CYII=")
When I try to append the canvas to the document, nothing is drawn either and I don't have any error thrown in the console.
What is the problem here ?
Here is my code :
var img = new Image();
img.src = "http://somerandomWebsite/picture.png";
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var context = canvas.getContext('2d');
context.drawImage(img, 0,0); // this doesn't seem to work
var dataURL = canvas.toDataURL(); // this will give me a lot of "A"
doSomething(dataURL);
Also, when doing a quick refresh, the image gets drawn correctly onto the canvas but I've got an error message in the console and dataURL is empty.
The message in Firefox is : "SecurityError: The operation is insecure.",
in Chrome it is "Uncaught SecurityError: Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported.",
and on IE I just get "SecurityError".
What does it mean ?
You have to wait that your image has loaded before you can paint it on the canvas.
To do so, simply use the load event handler of your <img> element :
// create a new image
var img = new Image();
// declare a function to call once the image has loaded
img.onload = function(){
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var context = canvas.getContext('2d');
context.drawImage(img, 0,0);
var dataURL = canvas.toDataURL();
// now you can do something with the dataURL
doSomething(dataURL);
}
// now set the image's src
img.src = "http://somerandomWebsite/picture.png";
Also, for the canvas' context.toDataURL() and context.getImageData to work properly, you have to get your image resource in a cross-origin compliant way, otherwise the canvas is "tainted" which means that any method to get pixels data will be blocked.
If your image comes from the same server, no problem.
If your image is served from an external server, be sure that it allows yours in its cross-origin headers and set the img.crossOrigin to "use-credentials".
If the server does allow anonymous requests, you can set the img.crossOrigin to "anonymous".
Nota Bene : CORS header is sent by the server, the cross-origin attribute will only let it know that you want to use CORS to get the image data, in no way you can circumvent it if the server is not set properly.
Also some UserAgents (IE & Safari) still haven't implemented this attribute.
Edge Case : If some of your images are from your server and some are from a CORS compliant one, then you may want to use the onerror event handler which should fire if you set the cross-origin attribute to "anonymous" on a non CORS server.
function corsError(){
this.crossOrigin='';
this.src='';
this.removeEventListener('error', corsError, false);
}
img.addEventListener('error', corsError, false);
I am trying to paint an image on a canvas before I get its dataURL(), but the data returned is like empty.
When I check it in the console, I see there is a lot of A in the string : ("data:image/png;base64,iVBO..some random chars... bQhfoAAAAAAAAAA... a lot of A ...AAAASUVORK5CYII=")
When I try to append the canvas to the document, nothing is drawn either and I don't have any error thrown in the console.
What is the problem here ?
Here is my code :
var img = new Image();
img.src = "http://somerandomWebsite/picture.png";
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var context = canvas.getContext('2d');
context.drawImage(img, 0,0); // this doesn't seem to work
var dataURL = canvas.toDataURL(); // this will give me a lot of "A"
doSomething(dataURL);
Also, when doing a quick refresh, the image gets drawn correctly onto the canvas but I've got an error message in the console and dataURL is empty.
The message in Firefox is : "SecurityError: The operation is insecure.",
in Chrome it is "Uncaught SecurityError: Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported.",
and on IE I just get "SecurityError".
What does it mean ?
You have to wait that your image has loaded before you can paint it on the canvas.
To do so, simply use the load event handler of your <img> element :
// create a new image
var img = new Image();
// declare a function to call once the image has loaded
img.onload = function(){
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
var context = canvas.getContext('2d');
context.drawImage(img, 0,0);
var dataURL = canvas.toDataURL();
// now you can do something with the dataURL
doSomething(dataURL);
}
// now set the image's src
img.src = "http://somerandomWebsite/picture.png";
Also, for the canvas' context.toDataURL() and context.getImageData to work properly, you have to get your image resource in a cross-origin compliant way, otherwise the canvas is "tainted" which means that any method to get pixels data will be blocked.
If your image comes from the same server, no problem.
If your image is served from an external server, be sure that it allows yours in its cross-origin headers and set the img.crossOrigin to "use-credentials".
If the server does allow anonymous requests, you can set the img.crossOrigin to "anonymous".
Nota Bene : CORS header is sent by the server, the cross-origin attribute will only let it know that you want to use CORS to get the image data, in no way you can circumvent it if the server is not set properly.
Also some UserAgents (IE & Safari) still haven't implemented this attribute.
Edge Case : If some of your images are from your server and some are from a CORS compliant one, then you may want to use the onerror event handler which should fire if you set the cross-origin attribute to "anonymous" on a non CORS server.
function corsError(){
this.crossOrigin='';
this.src='';
this.removeEventListener('error', corsError, false);
}
img.addEventListener('error', corsError, false);