找到一个按比例生成缩略图的代码，发与大家分享。

[php]
<?php
#########################################################
# #
# Release....: ImageVue.v1.4.PHP.NULL-WDYL #
# Date.......: 01/30/04 #
# Released...: WDYL #
# Protection.: CallHome, License Check, Refferer Links #
# URL........: http://www.imagevuex.com #
# #
#########################################################
$img=$_GET['img'];
$path = substr($img, 0, strrpos($img, '/'));
$file = substr($img, strrpos($img, '/') + 1);

$tnpath = $path . '/tn_' . $file;

if (@file_exists($tnpath)) {
Header("Content-type: image/jpeg");
readfile($tnpath);

} elseif (!file_exists($img)) {
die("Image doesn't exist");

} else {
if (function_exists("imagecreatefromjpeg") and function_exists("imagecreatetruecolor")) {
$orig_image = imagecreatefromjpeg($img);
$orig_x = imagesx($orig_image);
$orig_y = imagesy($orig_image);

if (($orig_x / $orig_y) >= (4 / 3)) {
$y = round($orig_y / ($orig_x / 158));
$x = 158;
} else {
$x = round($orig_x / ($orig_y / 118));
$y = 118;
}

$sm_image = imagecreatetruecolor($x, $y);
Imagecopyresampled($sm_image, $orig_image, 0, 0, 0, 0, $x, $y, $orig_x, $orig_y);
Header("Content-type: image/jpeg");
imageJPEG($sm_image, '', 80);
@imageJPEG($sm_image, $tnpath, 80);
imagedestroy ($sm_image);
imagedestroy ($orig_image);
} else {

header("Content-type: image/jpeg");
readfile ('thumb.jpg');
}
}
?>
[/php]