nepěkné miniatury

$size = GetImageSize( $images_dir."/".$filename );
                if($size[0] > $size[1])
                {
                    $thumbnail_width = 100;
                    $thumbnail_height = (int)(100 * $size[1] / $size[0]);
                }
                else
                {
                    $thumbnail_width = (int)(100 * $size[0] / $size[1]);
                    $thumbnail_height = 100;
                }
            
                // vytvoření miniatury pomoci GD
                $function_suffix = $gd_function_suffix[$filetype];
                $function_to_read = "ImageCreateFrom".$function_suffix;
                $function_to_write = "Image".$function_suffix;

                // přečtení zdroje
                $source_handle = $function_to_read ( $images_dir."/".$filename ); 
                
                if($source_handle)
                {
                         $destination_handle = ImageCreate ( $thumbnail_width, $thumbnail_height );
                
                    // změna velikosti
                      ImageCopyResized( $destination_handle, $source_handle, 0, 0, 0, 0, $thumbnail_width, $thumbnail_height, $size[0], $size[1] );
                }

                // uložení miniatury
                $function_to_write( $destination_handle, $images_dir."/tb_".$filename );
                ImageDestroy($destination_handle );