I have found a few different posts and even questions on stackoverflow answering this question. I am basically implementing this same thing as this post.
So here is my issue. When I upload the photo, I also need to submit the rest of the form. Here is my html:
<form id="uploadImageForm" enctype="multipart/form-data">
<input name="imagefile[]" type="file" id="takePictureField" accept="image/*" onchange="uploadPhotos(\'#{imageUploadUrl}\')" />
<input id="name" value="#{name}" />
... a few more inputs ...
</form>
Previously, I did not need to resize the image, so my javascript looked like this:
window.uploadPhotos = function(url){
var data = new FormData($("form[id*='uploadImageForm']")[0]);
$.ajax({
url: url,
data: data,
cache: false,
contentType: false,
processData: false,
type: 'POST',
success: function(data){
... handle error...
}
}
});
};
This all worked great... now that I need to resize the images... how can I replace the image in the form so that the resized one is posted and not the uploaded image?
window.uploadPhotos = function(url){
var resizedImage;
// Read in file
var file = event.target.files[0];
// Ensure it's an image
if(file.type.match(/image.*/)) {
console.log('An image has been loaded');
// Load the image
var reader = new FileReader();
reader.onload = function (readerEvent) {
var image = new Image();
image.onload = function (imageEvent) {
// Resize the image
var canvas = document.createElement('canvas'),
max_size = 1200,
width = image.width,
height = image.height;
if (width > height) {
if (width > max_size) {
height *= max_size / width;
width = max_size;
}
} else {
if (height > max_size) {
width *= max_size / height;
height = max_size;
}
}
canvas.width = width;
canvas.height = height;
canvas.getContext('2d').drawImage(image, 0, 0, width, height);
resizedImage = canvas.toDataURL('image/jpeg');
}
image.src = readerEvent.target.result;
}
reader.readAsDataURL(file);
}
// TODO: Need some logic here to switch out which photo is being posted...
var data = new FormData($("form[id*='uploadImageForm']")[0]);
$.ajax({
url: url,
data: data,
cache: false,
contentType: false,
processData: false,
type: 'POST',
success: function(data){
... handle error...
}
}
});
};
I've thought about moving the file input out of the form and having a hidden input in the form that I set the value of to the value of the resized image... But I'm wondering if I can just replace the image that is already in the form.
This question is related to
javascript
html
canvas
If some of you, like me, encounter orientation problems I have combined the solutions here with a exif orientation fix
https://gist.github.com/SagiMedina/f00a57de4e211456225d3114fd10b0d0
if any interested I've made a typescript version:
interface IResizeImageOptions {
maxSize: number;
file: File;
}
const resizeImage = (settings: IResizeImageOptions) => {
const file = settings.file;
const maxSize = settings.maxSize;
const reader = new FileReader();
const image = new Image();
const canvas = document.createElement('canvas');
const dataURItoBlob = (dataURI: string) => {
const bytes = dataURI.split(',')[0].indexOf('base64') >= 0 ?
atob(dataURI.split(',')[1]) :
unescape(dataURI.split(',')[1]);
const mime = dataURI.split(',')[0].split(':')[1].split(';')[0];
const max = bytes.length;
const ia = new Uint8Array(max);
for (var i = 0; i < max; i++) ia[i] = bytes.charCodeAt(i);
return new Blob([ia], {type:mime});
};
const resize = () => {
let width = image.width;
let height = image.height;
if (width > height) {
if (width > maxSize) {
height *= maxSize / width;
width = maxSize;
}
} else {
if (height > maxSize) {
width *= maxSize / height;
height = maxSize;
}
}
canvas.width = width;
canvas.height = height;
canvas.getContext('2d').drawImage(image, 0, 0, width, height);
let dataUrl = canvas.toDataURL('image/jpeg');
return dataURItoBlob(dataUrl);
};
return new Promise((ok, no) => {
if (!file.type.match(/image.*/)) {
no(new Error("Not an image"));
return;
}
reader.onload = (readerEvent: any) => {
image.onload = () => ok(resize());
image.src = readerEvent.target.result;
};
reader.readAsDataURL(file);
})
};
and here's the javascript result:
var resizeImage = function (settings) {
var file = settings.file;
var maxSize = settings.maxSize;
var reader = new FileReader();
var image = new Image();
var canvas = document.createElement('canvas');
var dataURItoBlob = function (dataURI) {
var bytes = dataURI.split(',')[0].indexOf('base64') >= 0 ?
atob(dataURI.split(',')[1]) :
unescape(dataURI.split(',')[1]);
var mime = dataURI.split(',')[0].split(':')[1].split(';')[0];
var max = bytes.length;
var ia = new Uint8Array(max);
for (var i = 0; i < max; i++)
ia[i] = bytes.charCodeAt(i);
return new Blob([ia], { type: mime });
};
var resize = function () {
var width = image.width;
var height = image.height;
if (width > height) {
if (width > maxSize) {
height *= maxSize / width;
width = maxSize;
}
} else {
if (height > maxSize) {
width *= maxSize / height;
height = maxSize;
}
}
canvas.width = width;
canvas.height = height;
canvas.getContext('2d').drawImage(image, 0, 0, width, height);
var dataUrl = canvas.toDataURL('image/jpeg');
return dataURItoBlob(dataUrl);
};
return new Promise(function (ok, no) {
if (!file.type.match(/image.*/)) {
no(new Error("Not an image"));
return;
}
reader.onload = function (readerEvent) {
image.onload = function () { return ok(resize()); };
image.src = readerEvent.target.result;
};
reader.readAsDataURL(file);
});
};
usage is like:
resizeImage({
file: $image.files[0],
maxSize: 500
}).then(function (resizedImage) {
console.log("upload resized image")
}).catch(function (err) {
console.error(err);
});
or (async/await):
const config = {
file: $image.files[0],
maxSize: 500
};
const resizedImage = await resizeImage(config)
console.log("upload resized image")
Source: Stackoverflow.com