php修改上传图片尺寸的方法

<?php
// this is the temporary file created by php
$uploadedfile = $_files['uploadfile']['tmp_name'];
// create an image from it so we can do the resize
$src = imagecreatefromjpeg($uploadedfile);
// capture the original size of the uploaded image
list($width,$height)=getimagesize($uploadedfile);
// for our purposes, i have resized the image to be
// 600 pixels wide, and maintain the original aspect
// ratio. this prevents the image from being "stretched"
// or "squashed". if you prefer some max width other than
// 600, simply change the $newwidth variable
$newwidth=600;
$newheight=($height/$width)*600;
$tmp=imagecreatetruecolor($newwidth,$newheight);
// this line actually does the image resizing, copying from the original
// image into the $tmp image
imagecopyresampled($tmp,$src,0,0,0,0,$newwidth,$newheight,$width,$height);
// now write the resized image to disk. i have assumed that you want the
// resized, uploaded image file to reside in the ./images subdirectory.
$filename = "images/". $_files['uploadfile']['name'];
imagejpeg($tmp,$filename,100);
imagedestroy($src);
imagedestroy($tmp);
// note: php will clean up the temp file it created when the request
// has completed.
?>