So I'm trying to display image on canvas using File Reader. But it won't work. I don't know where the problem is.
var canvas = document.getElementById("ourCanvas"),
context = canvas.getContext('2d'),
uploadedFile = document.getElementById('uploaded-file');
window.addEventListener('DOMContentLoaded', initImageLoader);
function initImageLoader() {
uploadedFile.addEventListener('change', handleManualUploadedFiles);
function handleManualUploadedFiles(ev){
var file = ev.target.files[0];
handleFile(file);
}
}
function handleFile(file) {
var imageType = /image.*/;
if(file.type.match(imageType)){
var reader = new FileReader();
reader.onloadend = function(event) {
var tempImageStore = new Image();
tempImageStore.onLoad = function(ev){
canvas.height = ev.target.height;
canvas.width = ev.target.width;
context.drawImage(ev.target, 0, 0);
}
tempImageStore.src = event.target.result;
}
reader.readAsDataURL(file);
}
}
After I upload the file, image don't show on the Canvas, and does'nt show anything wrong in Console. Is there any problem with my code?
I have a button where you can upload an image and insert it in a tag, it works on every browser but not on chrome. The first reader.onloadend is processed, I can log image and image.src.
var inputUpload = document.getElementById('buttonUpload');
inputUpload.addEventListener('change', (e) => {
const file = e.target.files[0];
const reader = new FileReader();
reader.onloadend = () => {
//Initiate the JavaScript Image object.
var image = new Image();
image.src = reader.result;
console.log('image.src');
image.onloadend = function() { /* execution stops here */
var height = this.height;
var width = this.width;
if (height > 150 || width > 150) {
showAlert('Image dimensions must be within 150×150 pixels.');
} else {
// convert file to base64 String
const base64String = reader.result.replace('data:', '').replace(/^.+,/, '');
// display image
valueImg = "data:image/png;base64," + base64String;
updateImg(valueImg);
};
};
};
reader.readAsDataURL(file);
});
<button id="buttonUpload" type="button" class="d-inline btn-custom mx-0">
Upload
</button>
When I select the image file, it stops at image.loadend but I get no errors in the console
I have the following function where user can upload an images and then compress them. The problem here is that when I console.log(e.target) inside the image.onload function, it displays it continuously in the console, meaning it is in a recursion and it freezes my app and it cannot do anything else.
This compression method I have taken from the following YouTube video and tried to adopt to what I have.
https://www.youtube.com/watch?v=bXf_UdyDzSA&ab_channel=Cod%C3%BACommunity
function addImageToForm(e) {
firebase.auth().onAuthStateChanged(function (user) {
if (user) {
let files = e.target.files;
if (numberOfImages + files.length > 4) {
alert("You can only upload at most 4 files!");
return;
}
numberOfImages += files.length;
for (let i = 0; i < files.length; i++) {
let file = files[i];
if (file) {
const reader = new FileReader();
reader.readAsDataURL(file);
reader.addEventListener("load", function (e) {
console.log(this);
let imageFile = e.target;
let divDocument = document.createElement("div");
let image = document.createElement("img");
divDocument.setAttribute("class", "id-document");
image.setAttribute("class", "image-preview");
image.setAttribute(
"style",
"width: inherit; height: inherit; border-radius: 20px;"
);
image.setAttribute("src", imageFile.result);
image.onload = function (e) {
let canvas = document.createElement("canvas");
let MAX_WIDTH = 200;
let scaleSize = MAX_WIDTH / e.target.width;
canvas.width = MAX_WIDTH;
canvas.height = e.target.height * scaleSize;
let ctx = canvas.getContext("2d");
ctx.drawImage(e.target, 0, 0, canvas.width, canvas.height);
console.log(e.target);
let srcEncoded = ctx.canvas.toDataURL(e.target, "image/jpeg");
image.setAttribute("src", srcEncoded);
}
divDocument.appendChild(image);
rowOfPhotos.appendChild(divDocument);
});
const reference = firebase
.storage()
.ref(`${user.displayName}/game_images/` + file.name);
reference
.put(file)
.then((snapshot) => snapshot.ref.getDownloadURL())
.then((url) => {
imagesArray.push(url);
});
} else {
image.style.display = null;
}
}
} else {
console.log("Not logged in");
}
});
}
Does anybody see where the problem is?
It's because, you change image src in onload function
image.setAttribute("src", srcEncoded);
Every time, image src is changed, onload function will be called.
I'm working on an Angular website, on a Image selector (in order to create thumbnail with set size).
I use a file input for the user to upload his file, then I catch the event, do some verification (format and size), and I process to it's resizing. But this is currently not working at all.
I'm actually making some promise that converts the FileInput target to a base64 image, then I use it to create an Image() object in order to access the image's width and height.
I'm changing img.width and img.height properties and creating back a FileInput with my img.src in it.
I can't really do however I want as I'm using ngx-image-cropper, and I really need to push a resized image in the cropper.
(ngx-image-cropper accepts FileEvent or Base64 img url)
// Proceed to the image resizing
resizeImg(img) {
if (img.width && img.height) {
if (img.height > img.width && img.height > 280) {
const coef = 280 / img.height;
img.width = img.width * coef;
img.height = img.height * coef;
} else if (img.width > img.height && img.width > 280) {
const coef = 280 / img.width;
img.height = img.height * coef;
img.width = img.width * coef;
}
}
console.log(img.width);
console.log(img.height);
return img;
}
// Creates back the FileInput
imageToFileInput(src, filename, imgType) {
return fetch(src)
.then(function(res) {
return res.arrayBuffer();
})
.then(function(buf) {
return new File([buf], filename, { type: imgType });
});
}
// Promise that creates an Image() object with file's base64 url
createImg(url) {
return new Promise(function(res, rej) {
const img = new Image();
img.onload = function() {
res(img);
};
img.src = url;
});
}
// Promise that generate the image file's base64 url
retrieveBase64Url(file) {
return new Promise(function(res, rej) {
const reader = new FileReader();
reader.onload = function() {
res(reader.result);
};
reader.readAsDataURL(file);
});
}
// Manages format/size errors then add file to cropper
fileProcess(fileInput: any) {
const file = fileInput.target.files[0];
this.preview = false;
if (
file &&
file.type !== 'image/png' &&
file.type !== 'image/jpg' &&
file.type !== 'image/jpeg'
) {
// Format error gesture
this.sizeError = false;
this.formatError = true;
} else if (file && file.size / 1000000 > this.maxSize) {
// Size error gesture
this.formatError = false;
this.sizeError = true;
} else {
this.fileName = file.name;
// Process to image resizing, apply it to file and then push it to the cropper
this.retrieveBase64Url(file).then(url => {
this.createImg(url).then(img => {
const resized_img = this.resizeImg(img);
this.imageToFileInput(resized_img.src, 'resized.png', 'image/png').then(result => {
this.imageChangedEvent = { target: { files: [result] } };
this.formatError = false;
this.sizeError = false;
});
});
});
}
}
I except the image to be resized before getting pushed in the cropper, but for now, even if it goes through all the resizing process, the image stays as it is when uploaded without the change in height and width.
I have a JPS with a form in which a user can put an image:
<div class="photo">
<div>Photo (max 240x240 and 100 kb):</div>
<input type="file" name="photo" id="photoInput" onchange="checkPhoto(this)"/>
</div>
I have written this js:
function checkPhoto(target) {
if(target.files[0].type.indexOf("image") == -1) {
document.getElementById("photoLabel").innerHTML = "File not supported";
return false;
}
if(target.files[0].size > 102400) {
document.getElementById("photoLabel").innerHTML = "Image too big (max 100kb)";
return false;
}
document.getElementById("photoLabel").innerHTML = "";
return true;
}
which works fine to check file type and size. Now I want to check image width and height but I cannot do it.
I have tried with target.files[0].width but I get undefined. With other ways I get 0.
Any suggestions?
The file is just a file, you need to create an image like so:
var _URL = window.URL || window.webkitURL;
$("#file").change(function (e) {
var file, img;
if ((file = this.files[0])) {
img = new Image();
var objectUrl = _URL.createObjectURL(file);
img.onload = function () {
alert(this.width + " " + this.height);
_URL.revokeObjectURL(objectUrl);
};
img.src = objectUrl;
}
});
Demo: http://jsfiddle.net/4N6D9/1/
I take it you realize this is only supported in a few browsers. Mostly firefox and chrome, could be opera as well by now.
P.S. The URL.createObjectURL() method has been removed from the MediaStream interface. This method has been deprecated in 2013 and superseded by assigning streams to HTMLMediaElement.srcObject. The old method was removed because it is less safe, requiring a call to URL.revokeOjbectURL() to end the stream. Other user agents have either deprecated (Firefox) or removed (Safari) this feature feature.
For more information, please refer here.
In my view the perfect answer you must required is
var reader = new FileReader();
//Read the contents of Image File.
reader.readAsDataURL(fileUpload.files[0]);
reader.onload = function (e) {
//Initiate the JavaScript Image object.
var image = new Image();
//Set the Base64 string return from FileReader as source.
image.src = e.target.result;
//Validate the File Height and Width.
image.onload = function () {
var height = this.height;
var width = this.width;
if (height > 100 || width > 100) {
alert("Height and Width must not exceed 100px.");
return false;
}
alert("Uploaded image has valid Height and Width.");
return true;
};
};
I agree. Once it is uploaded to somewhere the user's browser can access then it is pretty easy to get the size. As you need to wait for the image to load you'll want to hook into the onload event for img.
Updated example:
// async/promise function for retrieving image dimensions for a URL
function imageSize(url) {
const img = document.createElement("img");
const promise = new Promise((resolve, reject) => {
img.onload = () => {
// Natural size is the actual image size regardless of rendering.
// The 'normal' `width`/`height` are for the **rendered** size.
const width = img.naturalWidth;
const height = img.naturalHeight;
// Resolve promise with the width and height
resolve({width, height});
};
// Reject promise on error
img.onerror = reject;
});
// Setting the source makes it start downloading and eventually call `onload`
img.src = url;
return promise;
}
// How to use in an async function
(async() => {
const imageUrl = 'http://your.website.com/userUploadedImage.jpg';
const imageDimensions = await imageSize(imageUrl);
console.info(imageDimensions); // {width: 1337, height: 42}
})();
Older example:
var width, height;
var img = document.createElement("img");
img.onload = function() {
// `naturalWidth`/`naturalHeight` aren't supported on <IE9. Fallback to normal width/height
// The natural size is the actual image size regardless of rendering.
// The 'normal' width/height are for the **rendered** size.
width = img.naturalWidth || img.width;
height = img.naturalHeight || img.height;
// Do something with the width and height
}
// Setting the source makes it start downloading and eventually call `onload`
img.src = "http://your.website.com/userUploadedImage.jpg";
This is the easiest way to check the size
let img = new Image()
img.src = window.URL.createObjectURL(event.target.files[0])
img.onload = () => {
alert(img.width + " " + img.height);
}
Check for specific size. Using 100 x 100 as example
let img = new Image()
img.src = window.URL.createObjectURL(event.target.files[0])
img.onload = () => {
if(img.width === 100 && img.height === 100){
alert(`Nice, image is the right size. It can be uploaded`)
// upload logic here
} else {
alert(`Sorry, this image doesn't look like the size we wanted. It's
${img.width} x ${img.height} but we require 100 x 100 size image.`);
}
}
Attach the function to the onchange method of the input type file /onchange="validateimg(this)"/
function validateimg(ctrl) {
var fileUpload = ctrl;
var regex = new RegExp("([a-zA-Z0-9\s_\\.\-:])+(.jpg|.png|.gif)$");
if (regex.test(fileUpload.value.toLowerCase())) {
if (typeof (fileUpload.files) != "undefined") {
var reader = new FileReader();
reader.readAsDataURL(fileUpload.files[0]);
reader.onload = function (e) {
var image = new Image();
image.src = e.target.result;
image.onload = function () {
var height = this.height;
var width = this.width;
if (height < 1100 || width < 750) {
alert("At least you can upload a 1100*750 photo size.");
return false;
}else{
alert("Uploaded image has valid Height and Width.");
return true;
}
};
}
} else {
alert("This browser does not support HTML5.");
return false;
}
} else {
alert("Please select a valid Image file.");
return false;
}
}
const ValidateImg = (file) =>{
let img = new Image()
img.src = window.URL.createObjectURL(file)
img.onload = () => {
if(img.width === 100 && img.height ===100){
alert("Correct size");
return true;
}
alert("Incorrect size");
return true;
}
}
I think this may be the simplest for uploads if you want to use it other functions.
async function getImageDimensions(file) {
let img = new Image();
img.src = URL.createObjectURL(file);
await img.decode();
let width = img.width;
let height = img.height;
return {
width,
height,
}
}
Use like
const {width, height } = await getImageDimensions(file)
Suppose you were storing an image for Tiger taken in Kenya. So you could use it like to upload to cloud storage and then store photo information.
const addImage = async (file, title, location) => {
const { width, height } = await getImageDimensions(file)
const url = await uploadToCloudStorage(file) // returns storage url
await addToDatabase(url, width, height, title, location)
}
function validateimg(ctrl) {
var fileUpload = $("#txtPostImg")[0];
var regex = new RegExp("([a-zA-Z0-9\s_\\.\-:])+(.jpg|.png|.gif)$");
if (regex.test(fileUpload.value.toLowerCase())) {
if (typeof (fileUpload.files) != "undefined") {
var reader = new FileReader();
reader.readAsDataURL(fileUpload.files[0]);
reader.onload = function (e) {
var image = new Image();
image.src = e.target.result;
image.onload = function () {
var height = this.height;
var width = this.width;
console.log(this);
if ((height >= 1024 || height <= 1100) && (width >= 750 || width <= 800)) {
alert("Height and Width must not exceed 1100*800.");
return false;
}
alert("Uploaded image has valid Height and Width.");
return true;
};
}
} else {
alert("This browser does not support HTML5.");
return false;
}
} else {
alert("Please select a valid Image file.");
return false;
}
}
You can do the steps for previewing the image without showing it which is supported on all browsers. Following js code shows you how to check the width and height :
var file = e.target.files[0];
if (/\.(jpe?g|png|gif)$/i.test(file.name)) {
var reader = new FileReader();
reader.addEventListener("load", function () {
var image = new Image();
image.src = this.result as string;
image.addEventListener('load', function () {
console.log(`height: ${this.height}, width: ${this.width}`);
});
}, false);
reader.readAsDataURL(file);
}
Based on Mozilla docs:
The readAsDataURL method is used to read the contents of the specified
Blob or File. When the read operation is finished, the readyState
becomes DONE, and the loadend is triggered. At that time, the result
attribute contains the data as a data: URL representing the file's
data as a base64 encoded string.
And the browser compatibility is listed too.
In my case, I needed to also prevent the form from being submited, so here is the solution that worked for me.
The preventDefault will stop the form action, then we check the size and dimensions of the image in the onload function.
If all good, we allow the submit.
As the submit button gets disabled if a user still tries to submit the form with an invalid image, I also had to re-able the submit button once a valid image is inputted.
const validateMaxImageFileSize = (e) => {
e.preventDefault();
const el = $("input[type='file']")[0];
if (el.files && el.files[0]) {
const file = el.files[0];
const maxFileSize = 5242880; // 5 MB
const maxWidth = 1920;
const maxHeight = 1080;
const img = new Image();
img.src = window.URL.createObjectURL(file);
img.onload = () => {
if (file.type.match('image.*') && file.size > maxFileSize) {
alert('The selected image file is too big. Please choose one that is smaller than 5 MB.');
} else if (file.type.match('image.*') && (img.width > maxWidth || img.height > maxHeight)) {
alert(`The selected image is too big. Please choose one with maximum dimensions of ${maxWidth}x${maxHeight}.`);
} else {
e.target.nodeName === 'INPUT'
? (e.target.form.querySelector("input[type='submit']").disabled = false)
: e.target.submit();
}
};
}
};
$('form.validate-image-size').on('submit', validateMaxImageFileSize);
$("form.validate-image-size input[type='file']").on('change', validateMaxImageFileSize);
function uploadfile(ctrl) {
var validate = validateimg(ctrl);
if (validate) {
if (window.FormData !== undefined) {
ShowLoading();
var fileUpload = $(ctrl).get(0);
var files = fileUpload.files;
var fileData = new FormData();
for (var i = 0; i < files.length; i++) {
fileData.append(files[i].name, files[i]);
}
fileData.append('username', 'Wishes');
$.ajax({
url: 'UploadWishesFiles',
type: "POST",
contentType: false,
processData: false,
data: fileData,
success: function(result) {
var id = $(ctrl).attr('id');
$('#' + id.replace('txt', 'hdn')).val(result);
$('#imgPictureEn').attr('src', '../Data/Wishes/' + result).show();
HideLoading();
},
error: function(err) {
alert(err.statusText);
HideLoading();
}
});
} else {
alert("FormData is not supported.");
}
}