如何使用 php 和 html 在缩略图上创建圆角

func.php 文件，当图像上传到网站时，它会生成缩略图。 我了解如何使圆角半径为 5，但由于某种原因，我现在困惑在哪里将圆角合并到我的代码中，请帮助：

<?php
function create_thumb($directory, $image, $destination) {
  $image_file = $image;
  $image = $directory.$image;
if (file_exists($image)) {
$source_size = getimagesize($image);
if ($source_size !== false) {
  $thumb_width = 100;
  $thumb_height = 100;
  switch($source_size['mime']) {
    case 'image/jpeg':
         $source = imagecreatefromjpeg($image);
    break;
    case 'image/png':
         $source = imagecreatefrompng($image);
    break;
    case 'image/gif':
         $source = imagecreatefromgif($image);
    break;
  }
  $source_aspect = round(($source_size[0] / $source_size[1]), 1);
  $thumb_aspect = round(($thumb_width / $thumb_height), 1);
  if ($source_aspect < $thumb_aspect) {
    $new_size = array($thumb_width, ($thumb_width / $source_size[0]) * $source_size[1]);
    $source_pos = array(0, ($new_size[1] - $thumb_height) / 2);
  } else if ($source_aspect > $thumb_aspect) {
    $new_size = array(($thumb_width / $source_size[1]) * $source_size[0], $thumb_height);
    $source_pos = array(($new_size[0] - $thumb_width) / 2, 0);
  } else {
    $new_size = array($thumb_width, $thumb_height);
    $source_pos = array(0, 0);
  }
  if ($new_size[0] < 1) $new_size[0] = 1;
  if ($new_size[1] < 1) $new_size[1] = 1;
  $thumb = imagecreatetruecolor($thumb_width, $thumb_height);
  imagecopyresampled($thumb, $source, 0, 0, $source_pos[0], $source_pos[1], $new_size[0], $new_size[1], $source_size[0], $source_size[1]);
  switch($source_size['mime']) {
    case 'image/jpeg':
         imagejpeg($thumb, $destination.$image_file);
    break;
    case 'image/png':
          imagepng($thumb, $destination.$image_file);
    break;
    case 'image/gif':
         imagegif($thumb, $destination.$image_file);
    break;
  }

}
  }
}
?>