Develop Reference

How to make a base64 array from an array of photos

const arrUrl = [
'https://avatars.mds.yandex.net/getzen_doc/1714479/pub_5e4b9183baec8f365f1ff215_5e4b91c9bb4a6d368b8d9d4c/scale_1200',
'https://avatars.mds.yandex.net/getzen_doc/1714479/pub_5e4b9183baec8f365f1ff215_5e4b91c9bb4a6d368b8d9d4c/scale_1200',
'https://avatars.mds.yandex.net/getzen_doc/1714479/pub_5e4b9183baec8f365f1ff215_5e4b91c9bb4a6d368b8d9d4c/scale_1200',
'https://avatars.mds.yandex.net/getzen_doc/1714479/pub_5e4b9183baec8f365f1ff215_5e4b91c9bb4a6d368b8d9d4c/scale_1200'
];
there is an array of different links to photos, how to make them all in base64, I have a script that makes base64 photos, but I can't combine them
var img = new Image();
img.crossOrigin = 'Anonymous';
// The magic begins after the image is successfully loaded
img.onload = function () {
var canvas = document.createElement('canvas'),
ctx = canvas.getContext('2d');
canvas.height = img.naturalHeight;
canvas.width = img.naturalWidth;
ctx.drawImage(img, 0, 0);
// Unfortunately, we cannot keep the original image type, so all images will be converted to PNG
// For this reason, we cannot get the original Base64 string
var uri = canvas.toDataURL('image/png'),
b64 = uri.replace(/^data:image.+;base64,/, '');
console.log(b64); //-> "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQImWP4z8DwHwAFAAH/q842iQAAAABJRU5ErkJggg=="
};
// If you are loading images from a remote server, be sure to configure “Access-Control-Allow-Origin”
// For example, the following image can be loaded from anywhere.
var url = '//static.base64.guru/uploads/images/1x1.gif';
img.src = url;
or
https://gist.github.com/CawaKharkov/1c477d44fcfdf67aea3f/revisions#diff-7b3e9484330c338cea137079906c2390c4961003e07e3a9d13bed49d9d63805eR17

jpg loaded with python keras is different from jpg loaded in javascript

I am loading jpg image in python on the server. Then I am loading the same jpg image with javascript on the client. Finally, I am trying to compare it with the python output. But loaded data are different so images do not match. Where do I have a mistake?
Python code
from keras.preprocessing.image import load_img
from keras.preprocessing.image import img_to_array
filename = './rcl.jpg'
original = load_img(filename)
numpy_image = img_to_array(original)
print(numpy_image)
JS code
import * as tf from '#tensorflow/tfjs';
photo() {
var can = document.createElement('canvas');
var ctx = can.getContext("2d");
var img = new Image();
img.onload = function() {
ctx.drawImage(img, 0, 0);
};
img.crossOrigin = "anonymous";
img.src = './rcl.jpg';
var tensor = tf.fromPixels(can).toFloat();
tensor.print()
}

You are drawing the image on a canvas before rendering the canvas as a tensor. Drawing on a canvas can alter the shape of the initial image. For instance, unless specified otherwise - which is the case with your code - the canvas is created with a width of 300 px and a height of 150 px. Therefore the resulting shape of the tensor will be more or less something like the following [150, 300, 3].
1- Using Canvas
Canvas are suited to resize an image as one can draw on the canvas all or part of the initial image. In that case, one needs to resize the canvas.
const canvas = document.create('canvas')
// canvas has initial width: 300px and height: 150px
canvas.width = image.width
canvas.height = image.heigth
// canvas is set to redraw the initial image
const ctx = canvas.getContext('2d')
ctx.drawImage(image, 0, 0) // to draw the entire image
One word of caution though: all the above piece should be executed after the image has finished loading using the event handler onload as the following
const im = new Image()
im.crossOrigin = 'anonymous'
im.src = 'url'
// document.body.appendChild(im) (optional if the image should be displayed)
im.onload = () => {
const canvas = document.create('canvas')
canvas.width = image.width
canvas.height = image.heigth
const ctx = canvas.getContext('2d')
ctx.drawImage(image, 0, 0)
}
or using async/await
function load(url){
return new Promise((resolve, reject) => {
const im = new Image()
im.crossOrigin = 'anonymous'
im.src = 'url'
im.onload = () => {
resolve(im)
}
})
}
// use the load function inside an async function
(async() => {
const image = await load(url)
const canvas = document.create('canvas')
canvas.width = image.width
canvas.height = image.heigth
const ctx = canvas.getContext('2d')
ctx.drawImage(image, 0, 0)
})()
2- Using fromPixel on the image directly
If the image is not to be resized, you can directly render the image as a tensor using fromPixel on the image itself

Loading image and resizing through canvas causes infinite loop

I want to get an image scaled correctly after loading it with a dummy click on a <input type='file'> and compressing it via drawing it onto a canvas. When calling a console.log() inside the img.onload I discovered it was being run in a loop. Putting the img.src = canvas.toDataURL("image/png") outside of the onload results in a blank image but no loop. Moving things around by trial and error has not been effective as I don't get the dynamics at play here (even though I can get images redrawn when rescaling a canvas). Thanks!
$('button.picture').on('click',function(){
var outerWrapper = $(this).closest('.outerWrapper')
$(this).siblings('.imageLoad').on('change', function(e){
var loadedImage = e.target.files[0]
var img = new Image();
img.src = window.URL.createObjectURL(loadedImage);
var canvas = document.createElement("canvas");
canvas.width = outerWrapper.width()
canvas.height = outerWrapper.height()
img.onload = function(e){
//still here the img.width returns the canvas width and not the original image's width
console.log(img.width)
var context = canvas.getContext("2d");
context.drawImage(img,0,0, canvas.width, canvas.height )
img.src = canvas.toDataURL("image/png")
}
$(this).closest('.outerWrapper').children('.imageWrapper').append(img)
})
$(this).siblings('.imageLoad').trigger('click')
})

To answer my own question I want to make clear what my aims were:
Load in image through a dummy click on an <input type="file">
Keeps the aspect ratio of the original image
Compress it
What worked was not setting img.src = canvas.toDataURL("image/png") as you would when resizing a canvas but by loading the original again image with URL.createObjectURL(loadedImage). To preserve the aspect ration I had to create two separate images, one to get the img.naturalWidth and img.naturalHeight for calculation and the next to load the image onto the canvas. Works a charm. Would be interested to learn where it can be refined.
$('button.picture').on('click',function(){
var outerWrapper = $(this).closest('.outerWrapper')
$(this).siblings('.imageLoad').on('change', function(e){
var loadedImage = e.target.files[0]
var img = new Image();
img.src = window.URL.createObjectURL(loadedImage);
var canvasPic = $('<canvas class="canvasPic"></canvas>')
canvasPic.prependTo(outerWrapper)
var canvas = canvasPic[0]
canvas.width = outerWrapper.width()
canvas.height = outerWrapper.height()
var context = canvas.getContext("2d");
var image = new Image();
image.onload = function(){
var w = img.naturalWidth
var h = img.naturalHeight
var ratio = h/w
var newWidth = canvas.height/ratio
context.drawImage(img,0,0,newWidth,canvas.height)
}
image.src = URL.createObjectURL(loadedImage);
})
$(this).siblings('.imageLoad').trigger('click')
})

Javascript img to base64 don't load

I develop Photoshop extension that sends images to the server.
Edit: Extensions in photoshop build from html file that define the GUI, js file that basically is the same as any js file, but it's can also launch photoshop function and it is execute from photoshop.
I need to send the images from the file system of the user (from C:\path\to\images)
To encode the images I converted them to dataURL (base64).
The problem occurs in the first time that I convert the images to dataURL. But in the second time and so, it manages to convert the images and everything is fine. In the first time the image doesn't loaded.
I have a folder where the images are and I want to upload the pictures from there, I used a loop that runs on photos and set them into <img src=path> to and then it converts them based 64 via <canvas>.
My code:
function convertLayersToBase64(imgHeight, imgWidth){
var img = new Image();
images = [];
for (var i=0; i<=imagesLength; i++){
path = folder + "layer " + i +".png";
img.src = path;
var canvas = document.createElement("canvas");
canvas.height = imgHeight;
canvas.width = imgWidth;
var ctx = canvas.getContext("2d");
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.drawImage(img, 0, 0);
var dataURL = canvas.toDataURL();
images.push( dataURL );
}
return images;
}
I tried to delay the conversion by delay:
function delay(time) {
var d1 = new Date();
var d2 = new Date();
while (d2.valueOf() < d1.valueOf() + time) {
d2 = new Date();
}
}
JQuery when ready:
$(function(){
images.push(getBase64Image());
});
Img.complete
while(!img.complete)
continue;
(In the last example the code stuck in loop)
To put the function in:
img.onload = function(){
//the function here..
//when I use this method it succeed to convert
//only the last image.
}
Nothing worked..
I tried everything, please tell me what to change and how to fix that.
Edit: It's seem to me that the only way to load an image it's when the code

The function onload is an asynchronous action. You cannot just return images as the last statement within your convertLayersToBase64 function. You should either use promises, or a more simple approach would be to use a callback function.
function convertLayersToBase64(imgHeight, imgWidth, callback){
var images = [];
for (var i = 0; i <= imagesLength; i++) {
var img = new Image();
img.onload = function() {
var canvas = document.createElement("canvas");
canvas.height = imgHeight;
canvas.width = imgWidth;
var ctx = canvas.getContext("2d");
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.drawImage(this, 0, 0);
var dataURL = canvas.toDataURL();
images.push(dataURL);
if(images.length === imagesLength) {
callback(images);
}
}
path = folder + "layer " + i +".png";
img.src = path;
}
}
You would call this like:
convertLayersToBase64(200, 200, function(images) {
console.log('hii, i got images', images);
});
This is obviously without any form of error check, or even best practice guidelines, but I'll leave it up to you to implement that.

Unable to load an Image into Canvas and get base64 encoding for that image

I am trying to generate a PDF from HTML using jspdf plugin. I am stuck with loading Images into PDF. There is a function addImage() in plugin which takes base64 encoding of an image, but converting an image to base64 is not working.
I have used below two ways
//Create canvas, draw image in context and get the data url
imgToDataURL = function (img, outputFormat){
var canvas = document.createElement('canvas');
canvas.width = 20;
canvas.height = 20;
var c = canvas.getContext('2d');
c.height = img.height;
c.width=img.width;
c.drawImage(img, 0, 0);
c.save();
var dataurl = canvas.toDataURL(outputFormat);
return dataurl;
}
var img = new Image();
img.crossOrigin = 'Anonymous';
img.src = "image path"
img.height= 60;
img.width=60;
var dataURL = this.imgToDataURL(img,"image/jpeg");
renderer.pdf.addImage(dataURL, 'png',x+padding,y + this.internal.getLineHeight(),imageWidth,imageHeight);
This is printing wrong dataURL I am getting a white image. If I hard code the base64 code i.e return a hardcoded dataURL then addImage works fine. So the issue is with canvas.toDataURL which is giving me wrong output
this is the 2nd way
convertImgToBase64URL = function (url, callback, outputFormat){
var img = new Image();
img.crossOrigin = 'Anonymous';
img.onload = function(){
var canvas = document.createElement('CANVAS'),
ctx = canvas.getContext('2d'), dataURL;
canvas.height = this.height;
canvas.width = this.width;
ctx.drawImage(this, 0, 0);
dataURL = canvas.toDataURL(outputFormat);
callback(dataURL);
canvas = null;
};
img.src = url;
}
this.convertImgToBase64URL("Image Path",function(base64){
renderer.pdf.addImage(base64, 'PNG', 20, 20,48,48);
})
I have run this inside a javascript and the onload function is not even running I am not sure what is my mistake is.
Please suggest me what mistake I am doing in either way

In the first you missed assigning an onload function to your image. For that reason, the moment you try to create the dataURL, the image might not be loaded yet, ergo, the blank image. You could try changing the last few lines to this:
...
img.width=60;
img.onload = function () {
var dataURL = this.imgToDataURL(img,"image/jpeg");
renderer.pdf.addImage(dataURL, 'png',x+padding,y + this.internal.getLineHeight(),imageWidth,imageHeight);
}
img.src = "image path";
As for the second one, there seems to be a problem with the convertImgToBase64URL() which accepts 3 parameters, but you are passing 2. In you example, outputFormat parameter is undefined.