Download photos with EXIF data in browser

downloadPictureWithEXIFandRename.js

var piexif = require('piexif');

/* usage: 
downloadPictureWithEXIFandRename('https://images.unsplash.com/photo-1502120492606-fba13cc63721?ixlib=rb-0.3.5&ixid=eyJhcHBfaWQiOjEyMDd9&s=289f912c1f9e61361e64ac022a2a6ccc&auto=format&fit=crop&w=668&q=80', 'hello!')
*/
function downloadPictureWithEXIFandRename(pictureUrl, pictureName, callback) {
  var xhr = new XMLHttpRequest();
  var a = document.createElement('a');
  xhr.responseType = "arraybuffer";
  xhr.open('GET', pictureUrl, true);
  xhr.onload = function () {  //image/jpeg
    var base64_imgdata = arrayBufferToBase64(xhr.response);
    var exifimg = 'data:image/jpeg;base64,' + base64_imgdata;
    var exif = piexif.load(exifimg);
    var exifModified = piexif.insert(piexif.dump(exif), exifimg);
    var file = b64toBlob(exifModified.replace('data:image/jpeg;base64,', ''), 'image/jpeg')
    a.href = window.URL.createObjectURL(file);
    a.download = pictureName;  // Set to whatever file name you want
    // Now just click the link you created
    // Note that you may have to append the a element to the body somewhere
    // for this to work in Firefox
    a.click();
    a=null;xhr=null;
    callback && callback();
  }
  xhr.send()
}

function arrayBufferToBase64( buffer ) {
  var binary = '';
  var bytes = new Uint8Array( buffer );
  var len = bytes.byteLength;
  for (var i = 0; i < len; i++) {
      binary += String.fromCharCode( bytes[ i ] );
  }
  return window.btoa( binary );
}

function b64toBlob(b64Data, contentType, sliceSize) {
  contentType = contentType || '';
  sliceSize = sliceSize || 512;

  var byteCharacters = atob(b64Data);
  var byteArrays = [];

  for (var offset = 0; offset < byteCharacters.length; offset += sliceSize) {
    var slice = byteCharacters.slice(offset, offset + sliceSize);

    var byteNumbers = new Array(slice.length);
    for (var i = 0; i < slice.length; i++) {
      byteNumbers[i] = slice.charCodeAt(i);
    }

    var byteArray = new Uint8Array(byteNumbers);

    byteArrays.push(byteArray);
  }

  var blob = new Blob(byteArrays, { type: contentType });
  return blob;
}