phpGD库生成高质量缩略图(示例)

3. $FILENAME="image.thumb";

4. // 生成图片的宽度
5. $RESIZEWIDTH=400;
6. // 生成图片的高度
7. $RESIZEHEIGHT=400;

8. function ResizeImage($im,$maxwidth,$maxheight,$name){

9. $width = imagesx($im);
10. $height = imagesy($im);
11. if(($maxwidth && $width > $maxwidth) || ($maxheight && $height > $maxheight)){
12. if($maxwidth && $width > $maxwidth){
13. $widthratio = $maxwidth/$width;
14. $RESIZEWIDTH=true;
15. }
16. if($maxheight && $height > $maxheight){
17. $heightratio = $maxheight/$height;
18. $RESIZEHEIGHT=true;
19. }
20. if($RESIZEWIDTH && $RESIZEHEIGHT){
21. if($widthratio < $heightratio){
22. $ratio = $widthratio;
23. }else{
24. $ratio = $heightratio;
25. }
26. }elseif($RESIZEWIDTH){
27. $ratio = $widthratio;
28. }elseif($RESIZEHEIGHT){
29. $ratio = $heightratio;
30. }
31. $newwidth = $width * $ratio;
32. $newheight = $height * $ratio;
33. if(function_exists("imagecopyresampled")){
34. $newim = imagecreatetruecolor($newwidth, $newheight);
35. imagecopyresampled($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
36. }else{
37. $newim = imagecreate($newwidth, $newheight);
38. imagecopyresized($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
39. }
40. ImageJpeg ($newim,$name . ".jpg");
41. ImageDestroy ($newim);
42. }else{
43. ImageJpeg ($im,$name . ".jpg");
44. }
45. }

46. if($_FILES['image']['size']){

47. if($_FILES['image']['type'] == "image/pjpeg"){
48. $im = imagecreatefromjpeg($_FILES['image']['tmp_name']);
49. }elseif($_FILES['image']['type'] == "image/x-png"){
50. $im = imagecreatefrompng($_FILES['image']['tmp_name']);
51. }elseif($_FILES['image']['type'] == "image/gif"){
52. $im = imagecreatefromgif($_FILES['image']['tmp_name']);
53. }
54. if($im){
55. if(file_exists("$FILENAME.jpg")){
56. unlink("$FILENAME.jpg");
57. }
58. ResizeImage($im,$RESIZEWIDTH,$RESIZEHEIGHT,$FILENAME);
59. ImageDestroy ($im);
60. }
61. }
62. ?>

2，测试代码(demo.php)

2. /**
3. * PHP生成高质量缩略图
4. * by bbs.it-home.org
5. */
6. include('ResizeImage.php');
7. if(!empty($_POST)){
8. echo($FILENAME.".jpg?cache=".rand(0,999999));
9. }
10. ?>