I'm using a plugin (dom-to-image) to generate a SVG content from a div.
It returns me a dataURL like this:
data image/xml, charset utf-8, <svg...
If a put this on a <img src the image is shown to normally.
The intent is to grab this dataURL, convert it to base64 so I can save it as an image.png on a mobile app.
Is it possible?
I tryied this solution https://stackoverflow.com/a/28450879/1691609
But coudn't get to work.
The console fire an error about the dataUrl
TypeError: Failed to execute 'serializeToString' on 'XMLSerializer': parameter 1 is not of type 'Node'.
==== UPDATE :: PROBLEM EXPLANATION/HISTORY ====
I'm using Ionic Framework, so my project is an mobile app.
The dom-to-image is already working cause right now, its rendering a PNG through toPng function.
The problem is the raster PNG is a blurry.
So I thought: Maybe the SVG will have better quality.
And it IS!! Its 100% perfect, actually.
On Ionic, I'm using 2 step procedure to save the image.
After get the PNG generated by the dom-to-img(base64) dataURL, I convert it to a Blob and then save into device.
This is working, but the final result, as I said, is blurry.
Then with SVG maybe it will be more "high quality" per say.
So, in order to do "minimal" change on a process that s already working :D I just need to convert an SVG into base64 dataURL....
Or, as some of you explained to me, into something else, like canvas...
I don't know any much :/
===
Sorry for the long post, and I really, really thank your help guys!!
EDIT COUPLE OF YARS LATER
Use JS fiddle for a working example: https://jsfiddle.net/msb42ojx/
Note, if you don't own DOM content (images), and those images don't have CORS enabled for everyone (Access-Control-Allow-Origin header), canvas cant render those images
I'm not trying to find out why is your case not working, here is how I did when I had something similar to do:
get the image sourcce (dom-to-image result)
set up a canvas with that image inside (using the image source)
download the image from canvas in whatever image you like: png, jpeg whatever
by the way you can resize the image to a standard format
document.getElementById('mydownload').onclick= function(){
var wrapper = document.getElementById('wrapper');
//dom to image
domtoimage.toSvg(wrapper).then(function (svgDataUrl) {
//download function
downloadPNGFromAnyImageSrc(svgDataUrl);
});
}
function downloadPNGFromAnyImageSrc(src)
{
//recreate the image with src recieved
var img = new Image;
//when image loaded (to know width and height)
img.onload = function(){
//drow image inside a canvas
var canvas = convertImageToCanvas(img);
//get image/png from convas
var pngImage = convertCanvasToImage(canvas);
//download
var anchor = document.createElement('a');
anchor.setAttribute('href', pngImage.src);
anchor.setAttribute('download', 'image.png');
anchor.click();
};
img.src = src;
// Converts image to canvas; returns new canvas element
function convertImageToCanvas(image) {
var canvas = document.createElement("canvas");
canvas.width = image.width;
canvas.height = image.height;
canvas.getContext("2d").drawImage(image, 0, 0);
return canvas;
}
// Converts canvas to an image
function convertCanvasToImage(canvas) {
var image = new Image();
image.src = canvas.toDataURL("image/png");
return image;
}
}
#wrapper{
background: red;
color: blue;
}
<script src="https://rawgit.com/tsayen/dom-to-image/master/src/dom-to-image.js"></script>
<button id='mydownload'>Download DomToImage</button>
<div id="wrapper">
<img src="http://i.imgur.com/6GvKdxY.jpg"/>
<div> DUDE IS WORKING</div>
<img src="http://i.imgur.com/6GvKdxY.jpg"/>
</div>
I translated #SilentTremor's solution into React/JS-Class:
class SVGToPNG {
static convert = function (src) {
var img = new Image();
img.onload = function () {
var canvas = SVGToPNG.#convertImageToCanvas(img);
var pngImage = SVGToPNG.#convertCanvasToImage(canvas);
var anchor = document.createElement("a");
anchor.setAttribute("href", pngImage.src);
anchor.setAttribute("download", "image.png");
anchor.click();
};
img.src = src;
};
static #convertImageToCanvas = function (image) {
var canvas = document.createElement("canvas");
canvas.width = image.width;
canvas.height = image.height;
canvas.getContext("2d").drawImage(image, 0, 0);
return canvas;
};
static #convertCanvasToImage = function (canvas) {
var image = new Image();
image.src = canvas.toDataURL("image/png");
return image;
};
}
export default SVGToPNG;
Usage:
let dataUrl = someCanvas.toDataURL("image/svg+xml");
SVGToPNG.convert(dataUrl);
Related
For some reason,I can't use any xhr request in my webview,so all the src of img can be loaded when I open the html, but if I want to save them to a pdf using something like jsPDF, all the img will be missing because of xhr request fail.So I want to ask is there any way to convert img src to base64 after page loaded without xhr request? And after page loaded,I think the images are already downloaded, so is it possible to find it locally and convert to base64 then set them back to src?
maybe use canvas to change srcs to base64?
const images = document.querySelectorAll("img");
images.forEach(img => {
img.onload = function() {
const canvas = document.createElement("canvas");
const ctx = canvas.getContext("2d");
canvas.width = img.width;
canvas.height = img.height;
ctx.drawImage(img, 0, 0);
const dataURL = canvas.toDataURL("image/jpeg");
img.setAttribute("src", dataURL);
};
});
I want to save an image of the canvas tag, but when i try create an image from the canvas it tells me "SecurityError: The operation is insecure", which i believe is problems with the canvas coming from another domain than what im on. This canvas is a map which is generated with openlayers3.
var canvas = document.getElementsByClassName('ol-unselectable')[0];
var dataURL = canvas.toDataURL('image/png');
var window = window.open();
window.document.write('<img src='+dataURL+'/>');
I've also tried
canvas.toBlob(function(blob) {
saveAs(blob, 'map.png')
}
Is there an easy work around so the canvas is not tainted?
You tried write in new browser window from another window this is impossible without https protocol or localhost. But you can create new img in currently window.
var canvas = document.getElementsByClassName('ol-unselectable')[0];
var dataURL = canvas.toDataURL('image/png');
var img = new Image();
img.width = 1000;
img.height = 1000;
img.src = dataURL;
img.onload = function () {
document.body.append(img);
}
I'm trying to get a base64 version of a canvas in HTML5.
Currently, the base64 image that I get from the canvas is blank.
I have found similar questions for example this one:
HTML Canvas image to Base64 problem
However, the issue that I have is that because I am adding 2 images in the canvas, I cannot use the example provided in those answers as most of them are using single image.
I understand that I have to wait until the canvas image is loaded properly before trying to get the base64 image. But I don't know how in my case.
This is my code:
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
context.canvas.width = 1000;
context.canvas.height = 1000;
var imageObj1 = new Image();
imageObj1.src = "http://www.offthegridnews.com/wp-content/uploads/2017/01/selfie-psuDOTedu.jpg";
imageObj1.onload = function() {
context.drawImage(imageObj1, 0, 180, canvas.width, canvas.height);
};
var imageObj2 = new Image();
imageObj2.src = "http://www.publicdomainpictures.net/pictures/150000/velka/banner-header-tapete-145002399028x.jpg"
imageObj2.onload = function() {
context.drawImage(imageObj2, 0, 0, canvas.width, 180);
};
// get png data url
//var pngUrl = canvas.toDataURL();
var pngUrl = canvas.toDataURL('image/png');
// get jpeg data url
var jpegUrl = canvas.toDataURL('image/jpeg');
$('#base').val(pngUrl);
<div class="contents" style="overflow-x:hidden; overflow-y:scroll;">
<div style="width:100%; height:90%;">
<canvas id="myCanvas" class="snap" style="width:100%; height:100%;" onclick="takephoto()"></canvas>
</div>
</div>
<p>
This is the base64 image
</p>
<textarea id="base">
</textarea>
and this is a working FIDDLE:
https://jsfiddle.net/3p3e6Ldu/1/
Can someone please advice on this issue?
Thanks in advance.
EDIT:
As suggested in the comments bellow, i tried to use a counter and when the counter reaches a specific number, I convert the canvas to base64.
Like so:https://jsfiddle.net/3p3e6Ldu/4/
In both your examples (the one from the question and the one from the comments), the order of commands does not really respect the async nature of the task at hand.
In your later example, you should put the if( count == 2 ) block inside the onload callbacks to make it work.
However, even then you will run into the next problem: You are loading the images from different domains. You can still draw them (either into the canvas or using an <img> tag), but you are not able to access their contents directly. Not even with the detour of using the <canvas> element.
I changed to code so it would work, if the images are hosted on the same domain. I also used a function to load the image and promises to handle the callbacks. The direct way of using callbacks and a counting variable, seem error-prone to me. If you check out the respective fiddle, you will notice the SecurityError shown. This is the result of the aforementioned problem with the Same-Origin-Policy I mentioned.
A previous question of mine in a similar direction was about how to detect, if I can still read the contents of a <canvas> after adding some images.
const canvas = document.getElementById('myCanvas');
const context = canvas.getContext('2d');
context.canvas.width = 1000;
context.canvas.height = 1000;
// function to retrieve an image
function loadImage(url) {
return new Promise((fulfill, reject) => {
let imageObj = new Image();
imageObj.onload = () => fulfill(imageObj);
imageObj.src = url;
});
}
// get images
Promise.all([
loadImage("http://www.offthegridnews.com/wp-content/uploads/2017/01/selfie-psuDOTedu.jpg"),
loadImage("http://www.publicdomainpictures.net/pictures/150000/velka/banner-header-tapete-145002399028x.jpg"),
])
.then((images) => {
// draw images to canvas
context.drawImage(images[0], 0, 180, canvas.width, canvas.height);
context.drawImage(images[1], 0, 0, canvas.width, 180);
// export to png/jpg
const pngUrl = canvas.toDataURL('image/png');
const jpegUrl = canvas.toDataURL('image/jpeg');
// show in textarea
$('#base').val(pngUrl);
})
.catch( (e) => alert(e) );
I need to write a new HTML file from a string using file system, I'm using Cordova 2.4.0. . That HTML would have some images loaded from a local folder, so because I need just one file (a HTML without png/jpg images alongside it) I'm trying to encode this images and apply them through CSS as background images (The CSS code is embeded in the same String, future HTML file). Well, the way I make these modifications to the string is by using functions returns. For example:
padding-top: 5%; background-image: url(' + agregaImagenLocal('../img/ESTELAR.png') + '); background-color: white;
The function "agregaImagenLocal(pathToLocalImage)" :
function agregaImagenLocal(pathToLocalFile) {
var canvas = document.getElementById('canvasOculto');
var imagen = new Image(150,100);
canvas.width = imagen.width;
canvas.height = imagen.height;
var contextoCanvas = canvas.getContext('2d');
imagen.onload = function () {
contextoCanvas.drawImage(imagen, 0, 0);
urlImagenLocal = canvas.toDataURL();
}
imagen.src = pathToLocalFile;
return urlImagenLocal //???????
}
I was doing this without the "onload" event, so it returned a blank image. But with this function inside the "onload" I don't know how to return the base64 encoded image to the first function.
This is the function to convert an Image (by file path) to Base64:
function convertImgToBase64(url, callback, outputFormat){
var canvas = document.createElement('CANVAS');
var ctx = canvas.getContext('2d');
var img = new Image;
img.crossOrigin = 'Anonymous';
img.onload = function(){
canvas.height = img.height;
canvas.width = img.width;
ctx.drawImage(img,0,0);
var dataURL = canvas.toDataURL(outputFormat || 'image/png');
callback.call(this, dataURL);
// Clean up
canvas = null;
};
img.src = url;
}
Once the conversion is made, you can use jQuery to set the background CSS using the Base64 code.
var imageUrl = ""; //Your Local Image Path HERE
convertImgToBase64(imageUrl, function(base64Img){
$('.output').css("background-image", base64Img);
}
This will set the source of an element with the class 'output' to the base64 image.
I got a strange problem with the "DrawImage"-Methode of the Canvas element. With the following code I create the canvas and attache it to the "rightcanvas" div.
var rightcanvas = document.getElementById('rightcanvas');
rcanvas = document.createElement('canvas');
rcanvas.setAttribute('width', canvasLength);
rcanvas.setAttribute('height', canvasHeight);
rcanvas.setAttribute('id', 'rcanvas');
rightcanvas.appendChild(rcanvas);
And now I try to draw a Base64 encoded image.
var rcontext = rcanvas.getContext('2d');
var image = new Image();
image.src = 'data:image/png;base64,iVBOR....';
rcontext.drawImage(image,0,0);
The canvas will be created and attached. But the image will not be displayed.Does somebody know what the problem is? =(
You have to wait for the image to load before drawing it to the canvas.
var image = new Image();
image.onload = function() {
rcontext.drawImage(image, 0, 0);
}
image.src = 'data:image/png;base64,iVBOR....';