PHP 实现缩略图

<?php
header("Content-type: image/png");function resize_image($filename, $tmpname, $xmax, $ymax) 
{ $ext = explode(".", $filename); $ext = $ext[count($ext)-1]; //判断文件类型，获取不同的图像if($ext == "jpg" || $ext == "jpeg") $im = imagecreatefromjpeg($tmpname); elseif($ext == "png") $im = imagecreatefrompng($tmpname); elseif($ext == "gif") $im = imagecreatefromgif($tmpname); //获取原图的高度和宽度$x = imagesx($im); $y = imagesy($im); if($x <= $xmax && $y <= $ymax) return $im; //按比例缩放if($x >= $y) { $newx = $xmax; $newy = $newx * $y / $x; } else { $newy = $ymax; $newx = $x / $y * $newy; } //创建新图像$im2 = imagecreatetruecolor($newx, $newy); imagecopyresized($im2, $im, 0, 0, 0, 0, floor($newx), floor($newy), $x, $y); return $im2;
} 
//输出资源
imagejpeg(resize_image('nriven.jpg','riven.jpg',300,300));
?>