php生成图片缩略图的方法

function make_thumb($src,$dest,$desired_width)
{
 
  / read the source image /
  $source_image = imagecreatefromjpeg($src);
  $width = imagesx($source_image);
  $height = imagesy($source_image);
  / find the "desired height" of this thumbnail, relative to the desired width /
  $desired_height = floor($height($desired_width/$width));
  / create a new, "virtual" image /
  $virtual_image = imagecreatetruecolor($desired_width,$desired_height);
  / copy source image at a resized size /
  imagecopyresized($virtual_image,$source_image,0,0,0,0,$desired_width,$desired_height,$width,$height);
  / create the physical thumbnail image to its destination /
  imagejpeg($virtual_image,$dest, 83);
}