javascript - HTML5 - resize image and keep EXIF in resized image

Question

How can I resize an image (using an HTML5 canvas element) and keep the EXIF information from the original image? I can extract EXIF info from from original image but I don't know how to copy it to the resized image.

This is how I retrieve the resized image data to send to the server-side code:

canvas.toDataURL("image/jpeg", 0.7);

For EXIF retrieval, I'm using the exif.js library.

Answer 1

Working solution: ExifRestorer.js

Usage with HTML5 image resize:

function dataURItoBlob(dataURI) 
{
    var binary = atob(dataURI.split(',')[1]);
    var array = [];
    for(var i = 0; i < binary.length; i++) {
        array.push(binary.charCodeAt(i));
    }
    return new Blob([new Uint8Array(array)], {type: 'image/jpeg'});
}

And main code, taken as part of HTML5 resizer from this page: https://github.com/josefrichter/resize/blob/master/public/preprocess.js (but slightly modified)

var reader = new FileReader();

//reader.readAsArrayBuffer(file); //load data ... old version
reader.readAsDataURL(file);       //load data ... new version
reader.onload = function (event) {
// blob stuff
//var blob = new Blob([event.target.result]); // create blob... old version
var blob = dataURItoBlob(event.target.result); // create blob...new version
window.URL = window.URL || window.webkitURL;
var blobURL = window.URL.createObjectURL(blob); // and get it's URL

// helper Image object
var image = new Image();
image.src = blobURL;

image.onload = function() {

   // have to wait till it's loaded
   var resized = ResizeImage(image); // send it to canvas

   resized = ExifRestorer.restore(event.target.result, resized);  //<= EXIF  

   var newinput = document.createElement("input");
   newinput.type = 'hidden';
   newinput.name = 'html5_images[]';
   newinput.value = resized; // put result from canvas into new hidden input
   form.appendChild(newinput);
 };
};