I'm trying to extract image information from canvas data and display it in a .png file. Thus far I've been able to extract the Base64 information from the canvas using the toDataURL() method and create a blob object (which is correctly identified as a .png image) but the image is always blank. Any suggestions? Here's the code
var canvasData = markup.find('canvas');
var imageDataURL = canvasData[4].toDataURL("image/png");
var theData = atob(imageDataURL.substring('data:image/png;base64,'.length)), asArray = new Uint8Array(theData.length);
for (var i = 0, len = theData.length; i < len; ++i) {
asArray[i] = theData.charCodeAt(i);
}
var blob = new Blob([asArray.buffer], { type: 'image/png' }); saveAs(blob, 'export_' + Date.now() + '.png');
Interestingly the size is correct, the only thing missing is the actual image within the .png.
Assuming the saveAs function initiates a file download, you can take a shortcut by just assigning the data URL to an a element, set a.download to the desired file name, and using a.click() to start the file download:
function canvasToFile()
{
var canvas = document.getElementsByTagName('canvas')[0];
canvas.getContext("2d").drawImage(img, 0, 0);
var a = document.createElement('a');
a.href = canvas.toDataURL("image/png");
a.download = 'export_' + Date.now() + '.png';
a.style.display = 'none';
document.body.appendChild(a);
a.click();
}
// For demo:
var img = document.getElementsByTagName('img')[0];
img.crossOrigin = 'Anonymous';
img.addEventListener('load', canvasToFile);
img.src = 'http://lorempixel.com/400/400/';
<canvas width="400" height="400"/>
<img/>
In some browsers it is not necessary to append a to the DOM tree (hence the lines a.style.display = 'none'; and document.body.appendChild(a); could be omitted), but in others (Firefox for example, if I'm not mistaken) it is.
Related
I am trying to implement a download button for Internet Explorer users that will let them download a png file being displayed on a page.
The image is provided as a Data URL and displays normally on the page.
However, when the image is downloaded on Internet Explorer using the following code, only the upper half of the image gets downloaded.
I know the problem does not come from dataURLtoBlob() because reading the blob as a Data Url returns exactly the same original data.
Can anyone help me understand what's going on here? Thanks a lot for the help.
downloadButton.onclick = function () {
if (window.navigator.msSaveOrOpenBlob) {
var filename = "image.png";
var data = $('#qrCode').attr("href");
var blob = dataURLtoBlob(data);
console.log(data);
let reader = new FileReader();
reader.readAsDataURL(blob);
reader.onload = function() {
console.log(reader.result);
};
window.navigator.msSaveBlob(blob, filename);
}
}
function dataURLtoBlob(dataUrl) {
var arr = dataUrl.split(',');
var mime = arr[0].match(/:(.*?);/)[1];
var byteString = atob(arr[1]);
var arrayBuffer = new ArrayBuffer(byteString.length);
var ia = new Uint8Array(arrayBuffer);
for (var i = 0; i < byteString.length; i++) {
ia[i] = byteString.charCodeAt(i);
}
return new Blob([ia], { type: mime });
}
I managed to find a workaround for this issue by using an intermediate canvas.
var ieCanvas = document.getElementById("ieCanvas");
var ctx = ieCanvas.getContext("2d");
var img = document.getElementById("qrCodeImg");
ctx.drawImage(img, 0, 0);
var filename = "download.png";
window.navigator.msSaveBlob(ieCanvas.msToBlob(), filename);
To summarise:
QR Code PNG -> Blob -> msSaveBlob = Half of the image
QR Code PNG -> Canvas -> Blob -> msSaveBlob = Full image
I'm trying to pass a PDF file from the server and display it inside the browser, but the output comes out corrupted.
var blob = atob(data.Package);
console.log(blob);
var file = new Blob([blob], { type: "application/pdf" });
const fileURL = URL.createObjectURL(file);
window.open(fileURL);
Console log outputs something that appears to be correct PDF (just the beginning of output):
I'm saving a copy of the PDF on the server before transfer to make sure it is not corrupt and it works.
URL constructed with URL.createObjectURL(file) seems to be short:
blob:http://localhost:61631/ad749684-2992-4311-8b17-f382a7c687be
server side code:
Object doc = Convert.ToBase64String(_Document.DocumentStream.ToArray());
JObject response = new JObject(new JProperty("Package", JObject.FromObject(doc)));
return new AspResponse<Object>(response);
It looks like the issue is because you need to convert the PDF data into an actual byte array, then pass that into the Blob constructor. Try this:
function convertToByteArray(input) {
var sliceSize = 512;
var bytes = [];
for (var offset = 0; offset < input.length; offset += sliceSize) {
var slice = input.slice(offset, offset + sliceSize);
var byteNumbers = new Array(slice.length);
for (var i = 0; i < slice.length; i++) {
byteNumbers[i] = slice.charCodeAt(i);
}
const byteArray = new Uint8Array(byteNumbers);
bytes.push(byteArray);
}
return bytes;
}
var blob = atob(data.Package);
console.log(blob);
var file = new Blob(convertToByteArray(blob), { type: "application/pdf" });
const fileURL = URL.createObjectURL(file);
window.open(fileURL);
This solution worked for me, basically generating the pdf as a base64 string in the backend and rendering the content in an anchor tag for downloading the pdf file.
https://kainikhil.medium.com/nodejs-how-to-generate-and-properly-serve-pdf-6835737d118e
I have looked at quite a few samples of how people are getting their base 64 byte arrays into PDF but sadly none seem to be working for me. Looked at :
Javascript: Open PDF in new tab from byte array and how to convert byte array to pdf and download
my code is not really any different from what I can tell.
I have a JS-Fiddle here with test byte array data that I can confirm via different base64 encoders/decoders that it is valid.
I am hoping someone can see what I am doing wrong with it. I am using the atob() wrapper to decode the base64 string and it does appear to be doing it correctly. Thanks to anyone who has suggestions.
For those who would prefer to just look at it here:
function go() {
var data = byteData ;
// console.log(data);
var pdfData = atob(data);
console.log(pdfData)
var file = new Blob([pdfData], {type:'application/pdf'});
var fileUrl = URL.createObjectURL(file);
//open it via a link
var fileName = "test.pdf";
var a = document.createElement("a");
document.body.appendChild(a);
a.href = fileUrl;
a.download = fileName;
a.click();
//open it directly
window.open(fileUrl);
}
const byteData = "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";
you also need to convert your base64 string to arraybuffer.
function _base64ToArrayBuffer(base64) {
var binary_string = window.atob(base64);
var len = binary_string.length;
var bytes = new Uint8Array(len);
for (var i = 0; i < len; i++) {
bytes[i] = binary_string.charCodeAt(i);
}
return bytes.buffer;
}
from this convert base64 string to arraybuffer
and call it in your code sample like this :-
function go() {
var data = byteData ;
// console.log(data);
// HERE THIS CHANGE IN YOUR CODE
var pdfData = _base64ToArrayBuffer(data);
var file = new Blob([pdfData], {type:'application/pdf'});
var fileUrl = URL.createObjectURL(file);
//open it via a link
var fileName = "test.pdf";
var a = document.createElement("a");
document.body.appendChild(a);
a.href = fileUrl;
a.download = fileName;
a.click();
//open it directly
window.open(fileUrl);
}
this jsfiddle :- fiddle
The following code should be able to save and load .png image to/from local hard drive.
Saving works fine(at least in chrome) but loading produces wrong url and display nothing..
A little help would be really appreciated!
<html>
<head>
<title></title>
</head>
<body>
<img id="img" /><br>
<input type="button" value="Save" onclick="onSave()" /><br />
<input type="file" onchange="onOpen(event)" /><br />
<script>
onSave = function () {
var canvas = document.createElement("canvas");
canvas.width = 200;
canvas.height = 200;
var ctx = canvas.getContext("2d");
ctx.fillRect(0, 0, 100, 150);
var dataURL = canvas.toDataURL("image/png");
var img64 = dataURL.replace(/^data:image\/(png|jpg);base64,/, "");
var binaryImg = atob(img64);
var length = binaryImg.length;
var ab = new ArrayBuffer(length);
var ua = new Uint8Array(ab);
for (var i = 0; i < length; i++) {
ua[i] = binaryImg.charCodeAt(i);
}
var blob = new Blob([ab]);
var a = document.createElement("a");
a.download = 'Blob_img';
a.innerHTML = "Download File";
a.href = window.webkitURL.createObjectURL(blob);
a.style.display = 'none';
document.body.appendChild(a);
a.click();
};
onOpen = function (event) {
var fileReader = new FileReader();
fileReader.onload = function (event) {
var ab = event.target.result;
var ua = new Uint8Array(ab);
var binaryImg;
for (var i = 0; i < ua.length; i++) {
binaryImg += String.fromCharCode(ua[i]);
}
var img64 = btoa(binaryImg);
var image = new Image();
image.src = 'data:image/png;base64,' + img64;
var img = document.getElementById('img');
img.src = image.src;
}
fileReader.readAsArrayBuffer(event.target.files[0]);
};
</script>
</body>
</html>
Your "load" handler for your FileReader is declared without an event parameter. As a result, it's not going to have access to the file contents.
fileReader.onload = function (event) {
var ab = event.target.result;
Without that parameter, the symbol "event" would refer to the parameter of the enclosing function, and that one won't have the file contents.
Also, I think you don't need to do the base64 encoding/decoding via atob and btoa, because the results of converting the canvas contents to a data URL will be a base64 string anyway.
In case somebody is wondering, there is a simpler way of reading the file:
FileReader.readAsDataURL
Check a working example at https://developer.mozilla.org/en-US/docs/Web/API/FileReader.readAsDataURL.
I'm trying to write a file upload script for use in a secure corporate intranet and having just a little trouble...
In the following code, I get no errors and all my debugging looks like everything is working, but the end result is always a 'blank' image:
var ctx = document.createElement('canvas');
var img = new Image();
img.onload = function(){
ctx.drawImage(img,0,0);
}
img.src = $('#UpdateImage:file');
var imgStr = ctx.toDataURL("image/png", "");
document.getElementById("Item_Create_Image_Avatar").src = imgStr;
When I "inspect element" on the 'Item_Create_Image_Avatar' object, the 'src' value looks absolutely perfect:
<img src="data:image/png;base64,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" id="Item_Create_Image_Avatar" style="vertical-align:top">
Why is my image coming in as blank?
Found This.
Select a File to Load:
<input id="inputFileToLoad" type="file" onchange="loadImageFileAsURL();" />
<div id="imgTest"></div>
<script type='text/javascript'>
function loadImageFileAsURL(){
var filesSelected = document.getElementById("inputFileToLoad").files;
if (filesSelected.length > 0){
var fileToLoad = filesSelected[0];
var fileReader = new FileReader();
fileReader.onload = function(fileLoadedEvent) {
var srcData = fileLoadedEvent.target.result; // <--- data: base64
var divTest = document.getElementById("imgTest");
var newImage = document.createElement('img');
newImage.src = srcData;
divTest.innerHTML = newImage.outerHTML;
}
fileReader.readAsDataURL(fileToLoad);
}
}
</script>
EDIT:
Source: How to convert image into base64 string using javascript
If you want to get the Data URL of the image after it loaded, you should get the Data URL after it loaded
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
var img = new Image();
img.onload = function() {
ctx.drawImage(img, 0, 0);
imgStr = canvas.toDataURL("image/png", "");
document.getElementById("Item_Create_Image_Avatar").src = imgStr;
}
img.src = $('#UpdateImage:file');
EDIT: Included the rest of the code
EDIT2: Edited stupid error regarding canvas and its context