I'm trying to convert a SVG file to PNG by drawing it to canvas.
var svgToCanvas = function(svgElement) {
setNameSpaceOnEl(svgElement);
appendCSSRules(svgElement, getCssRules(svgElement));
var image = new Image();
// this is ugly but will do:
var svgXml = $('<div>').append($(svgElement).clone()).html();
var b64str = btoa(unescape(encodeURIComponent(svgXml)));
// var svgXml = new XMLSerializer().serializeToString(svgElement);
var defer = $q.defer();
image.onload = function() {
var canvas = document.createElement('canvas');
canvas.width = image.width;
canvas.height = image.height;
var context = canvas.getContext('2d');
context.drawImage(image, 0, 0);
defer.resolve(canvas);
};
image.src = 'data:image/svg+xml;base64,' + b64str;
return defer.promise;
};
The problem is that even though the image handling takes place inside the onload function, Firefox yields error NS_ERROR_NOT_AVAILABLE: ... on the line
context.drawImage(image, 0, 0);.
With breakpoints I see the image.src at this point is a valid base64 string, and I can even open up the image itself.
The code above works in Chrome, but not in Firefox. Any suggestions how to get around this in Firefox?
Related
Converting image to the canvas with canvas.drawImage fails(but not throws err), the canvas looks transparent empty image
It doesn't happen for all image files I could not figure out which property of the image causes this but I uploaded an example photo with this issue
I started having this problem with chrome v83-v84
firefox works fine.
I want to upload a specified photo (its inside fiddle) and want to make canvas and draw canvas from the uploaded image and display it on chrome (chrome version should bigger or equal v85)
function testimg(src) {
var img = document.createElement("img");
img.src = src;
document.querySelector('#test').appendChild(img)
}
$('#file').on('change', fileAdded)
function fileAdded(event) {
var reader = new FileReader;
reader.onload = function () {
var image = new Image();
image.src = reader.result;
image.onload = function () {
document.querySelector('#test').appendChild(this)
var imgToSend = processImg(this, this.width, this.height);
testimg(imgToSend)
};
};
reader.readAsDataURL(event.currentTarget.files[0]);
}
function processImg(image, srcWidth, srcHeight) {
var canvas = document.createElement('canvas');
canvas.width = srcWidth;
canvas.height = srcHeight;
var ctx = canvas.getContext("2d");
ctx.drawImage(image, 0, 0);
ctx.fill();
return canvas.toDataURL();
}
https://jsfiddle.net/msacar/2Lgmc85t/24/
I have a problem with converting svg to png(base64).
Svg to base64 works fine, because it displays just fine in the browser.
But when i try to load in the image, it won't load. Anybody might have an idea why?
var xml = new XMLSerializer().serializeToString(svg);
var svg64 = btoa(xml);
var b64start = 'data:image/svg+xml;base64,';
var image64 = b64start + svg64;
console.log(image64);
const img = new Image();
img.onload = function() {
const canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
const ctx = canvas.getContext('2d');
ctx.drawImage(img, 0, 0);
const dataBase64 = canvas.toDataURL('image/png');
console.log(dataBase64);
generatePowerpoint(response, dataBase64);
}
img.onerror = function() {
console.log(this.src);
}
img.src = image64;
It depends of the browser you are using. Using Firefox, the svg tag must have width and height attributes (unit not in %).
It also depends of the content of the svg. If the svg contains non-latin characters, btoa may fail (even if it seems not to be the problem here since Svg to base64 works fine in your case).
I have a image here : https://tx3.travian.fr/hero_body.php?uid=446, by using a userscript (with Tampermonkey) I know how to read pixel data but this script runs on the page itself, so it has to be open :
var img = $('img')[0];
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
canvas.getContext('2d').drawImage(img, 0, 0, img.width, img.height);
var pixelData = canvas.getContext('2d').getImageData(195, 56, 1, 1).data;
If possible, I want to achieve that from another page of the website, make a get call and manipulate the img, but I only get weird data (unknown encoding or something else) and I don't know how to deal with the result :
$.get(link , function( data ) {
// test 1
//let obj = $(data).find('img');
// test 2
$$("#content").html('<img src="data:image/png;base64,' + data + '" />');
// test 3
let img = data;
let canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
canvas.getContext('2d').drawImage(img, 0, 0, img.width, img.height);
var pixelData = canvas.getContext('2d').getImageData(195, 56, 1, 1).data;
});
The image is well-load, i can see in "preview" tab, and everything is ok here :
But then how to deal with it :
Edit
$.get( link, function( data ) {
var canvas = document.createElement('canvas');
var ctx = canvas.getContext("2d");
var image = new Image();
image.onload = function() {
ctx.drawImage(this, 0, 0);
};
image.src = "data:image/png;base64," + data; // ERROR GET data:image/png;base64,%EF%B ... F%BD net::ERR_INVALID_URL
});
To try : just open the dev console on the login page https://tx3.travian.fr/ and execute (the img page does not require login) :
$.get("/hero_body.php?uid=446" , function( data ) { console.log(data) });
There is no reason to make an AJAX call to get the image, and as you have seen, making the AJAX call has problems, although it is possible. Just load the image as an image, draw it into a Canvas, and proceed as before.
const link = "https://tx3.travian.fr/hero_body.php?uid=446";
var img = new Image();
img.onload = function() {
var canvas = document.createElement('canvas');
canvas.width = this.naturalWidth;
canvas.height = this.naturalHeight;
var ctx = canvas.getContext('2d');
ctx.drawImage(this, 0, 0);
var pixelData = canvas.getContext('2d').getImageData(200, 200, 1, 1).data;
console.log('pixelData', pixelData);
}
img.src = link
Note that this is subject to Same Origin Policy limitations, but if you are accessing the image from a page on the same domain, that will not be an issue. (Otherwise you need to have an appropriate CORS policy on the image and set img.crossOrigin = "Anonymous".)
Note to readers: to run the code above while avoiding CORS issues, open the image link in your browser and then run the code in your browser's JavaScript console for that page.
I have two main questions. I'm trying to resize a base64 image according to the answer in
JavaScript reduce the size and quality of image with based64 encoded code
This seemed simple enough, except for the fact that I need to get only the base64 string from that function, without the data:image... header.
I tried to modify the function like this:
function resizeBase64Img(base64, width, height) {
var canvas = document.createElement("canvas");
canvas.width = width;
canvas.height = height;
var context = canvas.getContext("2d");
var deferred = $.Deferred();
$("<img/>").attr("src", "data:image/gif;base64," + base64).load(function () {
context.scale(width / this.width, height / this.height);
context.drawImage(this, 0, 0);
deferred.resolve($("<img/>").attr("src", canvas.toDataURL()));
});
var result = canvas.toDataURL();
return result.substr(result.indexOf(",") + 1)
}
which returns a base64 string. This string is corrupted, and it never displays correctly. Why is this happening and how can I fix it?
The other question is, is there a way to resize the image based on percentage and not on pixel size?
Thanks
I ended up rewriting the function based on another canvas function I found. This function takes the src of a base64 img, modifies the size and assigns the result in base64 to another element:
function resizeBase64Img(url, width, height) {
var img = new Image();
img.setAttribute('crossOrigin', 'anonymous');
img.onload = function () {
var canvas = document.createElement("canvas");
canvas.width = width;
canvas.height = height;
var ctx = canvas.getContext("2d");
ctx.scale(width/this.width, height/this.height);
ctx.drawImage(this, 0, 0);
result=canvas.toDataURL();
$('#ASSIGNEDELEMENT').val(result.substr(result.indexOf(",") + 1));
};
img.src = url;
}
And it should be invoked like this:
resizeBase64Img($('#image').attr('src'),300,300);
I need images to be copied and sent to server for image rotations etc.
To copy an image I'm using this code( from Get image data in JavaScript?):
function getBase64Image(img) {
// Create an empty canvas element
var canvas = document.createElement("canvas");
canvas.width = img.width;
canvas.height = img.height;
var ctx = canvas.getContext("2d");
ctx.drawImage(img, 0, 0);
var dataURL = canvas.toDataURL("image/png");
var replaced = dataURL.replace(/^data:image\/(png|jpg);base64,/, "");
console.log("dataurl=",dataURL);
console.log("replaced=",replaced);
return replaced;
}
It is called like this:
$("#xyz").load(send_image).each(function () {
if (this.complete)
$(this).load();
});
function send_image(){
getBase64Image(document.getElementById('xyz'));
}
However in getBase64Image function once in 40-50 times dataURL is being returned as empty.
What could be the reason?