1. <?php
2. /** 
3. * 生成缩略图 
4. * $srcName----为原图片路径 
5. * $newWidth，$newHeight----分别缩略图的最大宽，高 
6. * $newName----为缩略图文件名（含路径），默认为加入thumbnail 
7. * @param string $srcName 
8. * @param int $newWidth 
9. * @param int $newHeight 
10. * @param string $newName 
11. * return viod 
12. */ 
13. function resizeImg($srcName,$newWidth,$newHeight,$newName="") 
14. { 
15.         if($newName=="") 
16.         { 
17.                 $nameArr=explode('.',$srcName); 
18.                 $expName=array_pop($nameArr); 
19.                 $expName='thumbnail.'.$expName; 
20.                 array_push($nameArr,$expName); 
21.                 $newName = implode('.',$nameArr); 
22.         } 
23.         $info = ""; 
24.         $data = getimagesize($srcName,$info); 
25.         switch ($data[2]) 
26.         { 
27.                 case 1: 
28.                         if(!function_exists("imagecreatefromgif")){ 
29.                                 echo "你的GD库不能使用GIF格式的图片，请使用Jpeg或PNG格式！返回"; 
30.                                 exit(); 
31.                         } 
32.                         $im = ImageCreateFromGIF($srcName); 
33.                         break; 
34.                 case 2: 
35.                         if(!function_exists("imagecreatefromjpeg")){ 
36.                                 echo "你的GD库不能使用jpeg格式的图片，请使用其它格式的图片！返回"; 
37.                                 exit(); 
38.                         } 
39.                         $im = ImageCreateFromJpeg($srcName); 
40.                         break; 
41.                 case 3: 
42.                         $im = ImageCreateFromPNG($srcName); 
43.                         break; 
44.         } 
45.         $srcW=ImageSX($im); 
46.         $srcH=ImageSY($im); 
47.         $newWidthH=$newWidth/$newHeight; 
48.         $srcWH=$srcW/$srcH; 
49.         if($newWidthH<=$srcWH){ 
50.                 $ftoW=$newWidth; 
51.                 $ftoH=$ftoW*($srcH/$srcW); 
52.         } 
53.         else{ 
54.                 $ftoH=$newHeight; 
55.                 $ftoW=$ftoH*($srcW/$srcH); 
56.         } 
57.         if($srcW>$newWidth||$srcH>$newHeight) 
58.         { 
59.                 if(function_exists("imagecreatetruecolor")) 
60.                 { 
61.                         @$ni = ImageCreateTrueColor($ftoW,$ftoH); 
62.                         if($ni) ImageCopyResampled($ni,$im,0,0,0,0,$ftoW,$ftoH,$srcW,$srcH); 
63.                         else 
64.                         { 
65.                                 $ni=ImageCreate($ftoW,$ftoH); 
66.                                 ImageCopyResized($ni,$im,0,0,0,0,$ftoW,$ftoH,$srcW,$srcH); 
67.                         } 
68.                 } 
69.                 else 
70.                 { 
71.                         $ni=ImageCreate($ftoW,$ftoH); 
72.                         ImageCopyResized($ni,$im,0,0,0,0,$ftoW,$ftoH,$srcW,$srcH); 
73.                 } 
74.                 if(function_exists('imagejpeg')) ImageJpeg($ni,$newName); 
75.                 else ImagePNG($ni,$newName); 
76.                 ImageDestroy($ni); 
77.         } 
78.         ImageDestroy($im); 
79. } 
80. //开源代码phpfensi.com 
81. resizeImg('123.JPG',150,150); 
82. ?> 
83.  

原文链接：http://www.phpfensi.com/php/20140820/4510.html