PHP method to implement the function of generating image thumbnails based on GD library

This article mainly introduces the function of generating image thumbnails implemented by PHP based on the GD library, involving PHP's operation skills related to image attributes. Friends in need can refer to the following

The example of this article describes the PHP based on the GD library Implemented function to generate image thumbnails. Share it with everyone for your reference, the details are as follows:

<?php
/**
 * 生成缩略图函数（支持图片格式：gif、jpeg、png和bmp）
 * @author ruxing.li
 * @param string $src   源图片路径
 * @param int  $width  缩略图宽度（只指定高度时进行等比缩放）
 * @param int  $width  缩略图高度（只指定宽度时进行等比缩放）
 * @param string $filename 保存路径（不指定时直接输出到浏览器）
 * @return bool
 */
function mkThumbnail($src, $width = null, $height = null, $filename = null) {
  if (!isset($width) && !isset($height))
    return false;
  if (isset($width) && $width <= 0)
    return false;
  if (isset($height) && $height <= 0)
    return false;
  $size = getimagesize($src);
  if (!$size)
    return false;
  list($src_w, $src_h, $src_type) = $size;
  $src_mime = $size[&#39;mime&#39;];
  switch($src_type) {
    case 1 :
      $img_type = &#39;gif&#39;;
      break;
    case 2 :
      $img_type = &#39;jpeg&#39;;
      break;
    case 3 :
      $img_type = &#39;png&#39;;
      break;
    case 15 :
      $img_type = &#39;wbmp&#39;;
      break;
    default :
      return false;
  }
  if (!isset($width))
    $width = $src_w * ($height / $src_h);
  if (!isset($height))
    $height = $src_h * ($width / $src_w);
  $imagecreatefunc = &#39;imagecreatefrom&#39; . $img_type;
  $src_img = $imagecreatefunc($src);
  $dest_img = imagecreatetruecolor($width, $height);
  imagecopyresampled($dest_img, $src_img, 0, 0, 0, 0, $width, $height, $src_w, $src_h);
  $imagefunc = &#39;image&#39; . $img_type;
  if ($filename) {
    $imagefunc($dest_img, $filename);
  } else {
    header(&#39;Content-Type: &#39; . $src_mime);
    $imagefunc($dest_img);
  }
  imagedestroy($src_img);
  imagedestroy($dest_img);
  return true;
}
$result = mkThumbnail(&#39;./IMG_3324.JPG&#39;, 147, 147);

Note: Remember to turn on the GD library support first

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