Finally i found a solution using new WP_Image_Editor
I modified tiled-gallery.php start at line 207, the code below :
$new_img_path = image_resize( $file_path, $width, $height, $crop );
$new_img_size = getimagesize( $new_img_path );
$new_img = str_replace( basename( $image_src[0] ), basename( $new_img_path ), $image_src[0] );
…should be something like :
$new_img = '';
$new_img_size = array(
0 => 0,
1 => 0
);
$image = WP_get_image_editor( $file_path );
if ( ! is_wp_error( $image ) ) {
$image->resize( $width, $height, $crop );
$saved_image = $image->save();
$new_img = str_replace( basename( $image_src[0] ), basename( $saved_image['path'] ), $image_src[0] );
$new_img_size[0] = $new_img['width'];
$new_img_size[1] = $new_img['height'];
}
Works fine…