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);}