php生成图片缩略图的方法

/ 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,$source_image,$desired_width,$desired_height,$width,$height);
/ create the physical thumbnail image to its destination */
imagejpeg($virtual_image,83);
}