Simple PHP thumbnail generation function

A simple thumbnail generation function supports image formats: gif, jpeg, png and bmp. It supports scaling to a fixed size or proportional scaling. It supports direct input to the browser or saving to a file.

/**
 * Simple function to generate thumbnails (supports image formats: gif, jpeg, png and bmp)
 * @author xiaoshuoit@163.com
 * @param string $src source image path
 * @param int $width thumbnail width (Perform proportional scaling when only height is specified)
 * @param int $width Thumbnail height (conformal scaling is performed when only width is specified)
 * @param string $filename Save path (directly output to the browser when not specified)
 * @return bool
*/
function simple_thumb($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 = $size['mime' ];
 switch($src_type) {
 case 1 :
 $img_type = 'gif';
 break;
 case 2 :
 $img_type = 'jpeg';
 break;
 case 3 :
 $img_type = 'png' ;
 break;
 case 15 :
 $img_type = 'wbmp';
 break;
 default :
 return false;
 }

 if (!isset($width))
 $width = $src_w * ($height / $src_h);
 if (!isset($height))
 $height = $src_h * ($width / $src_w);

 $imagecreatefunc = 'imagecreatefrom' . $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 = 'image' . $img_type;
 if ($filename) {
 $imagefunc($dest_img, $filename);
 } else {
 header('Content-Type: ' . $src_mime);
 $imagefunc($dest_img) ;
 }

 imagedestroy($src_img);
 imagedestroy($dest_img);
 return true;
}

simple_thumb("http://www.baidu.com/img/bdlogo.gif", 100);
 //simple_thumb("img/example.jpg", 100, null , 'img/example_thumb.jpg');