functions.php

function upandup_ajax_cropper_upload() {
  $response = array();
  if ( check_ajax_referer( 'upandup_cropper_nonce', 'nonce', false ) ) {
    $uploads = wp_upload_dir();
    $uploadPath = trailingslashit( $uploads['path'] );
    $uploadURL = trailingslashit( $uploads['url'] );
    // get and sanitize global variables
    if ( isset( $_POST['sessionID'] ) ) {
      $sessionID = sanitize_text_field( $_POST['sessionID'] );
      $uploadPath .= $sessionID . '/';
      $uploadURL .= $sessionID . '/';
      // create folder if it doesn't exist
      if ( ! file_exists( $uploadPath ) ) {
        mkdir( $uploadPath, 0757, true);
      }
    }
    if ( isset( $_POST['imageData'] ) ) {
      // convert imageData to a jpg and save to the server.
      $imageData = sanitize_text_field( $_POST['imageData'] );
      $imageData = str_replace( 'data:image/png;base64,', '', $imageData );
      $imageData = str_replace( ' ', '+', $imageData );
      $imageData = base64_decode( $imageData );

      $filename = 'final-crop.jpg';
      $filePath = $uploadPath . $filename;
      $fileURL = $uploadURL . $filename;

      $image = imagecreatefromstring( $imageData );
      imagealphablending( $image, true );
      imagesavealpha( $image, true );
      imagejpeg( $image, $filePath, 100 );
      imagedestroy( $image );
      $response = array( 'success' => true, 'url' => $fileURL, 'path' => $filePath );
    }
  } else {
    $response = array( 'success' => false, 'error' => 'invalid nonce');
  }
  // return response
  header('Content-Type: application/json');
  echo json_encode( $response );
  die();
}
add_action( 'wp_ajax_cropper_upload', 'upandup_ajax_cropper_upload' );
add_action( 'wp_ajax_nopriv_cropper_upload', 'upandup_ajax_cropper_upload' );