php gd库实现图片大小裁剪与缩放

2. //图片裁剪、缩放函数
3. //$filepath图片路径,$percent缩放百分比
4. function imagepress($filepath,$percent='0.5'){
5. // 图片类型
6. header('Content-Type: image/jpeg');
7. // 获得新的图片大小
8. list($width, $height) = getimagesize($filepath);
9. $new_width = $width * $percent;
10. $new_height = $height * $percent;
11. // 重新取样
12. $image_p = imagecreatetruecolor($new_width, $new_height);
13. $image = imagecreatefromjpeg($filepath);
14. imagecopyresampled($image_p, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
15. // 输出
16. return imagejpeg($image_p, null, 100);
17. }

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原图:

效果图:

例子：

3. //$filepath图片路径,$new_width新的宽度,$new_height新的高度

4. function imagepress($filepath, $new_width, $new_height)
5. {
6. $source_info = getimagesize($filepath);
7. $source_width = $source_info[0];
8. $source_height = $source_info[1];
9. $source_mime = $source_info['mime'];
10. $source_ratio = $source_height / $source_width;
11. $target_ratio = $new_height / $new_width;

12. // 源图过高

13. if ($source_ratio > $target_ratio)
14. {
15. $cropped_width = $source_width;
16. $cropped_height = $source_width * $target_ratio;
17. $source_x = 0;
18. $source_y = ($source_height - $cropped_height) / 2;
19. }
20. // 源图过宽
21. elseif ($source_ratio {
22. $cropped_width = $source_height / $target_ratio;
23. $cropped_height = $source_height;
24. $source_x = ($source_width - $cropped_width) / 2;
25. $source_y = 0;
26. }
27. // 源图适中
28. else
29. {
30. $cropped_width = $source_width;
31. $cropped_height = $source_height;
32. $source_x = 0;
33. $source_y = 0;
34. }
35. switch ($source_mime)
36. {
37. case 'image/gif':
38. $source_image = imagecreatefromgif($filepath);
39. break;
40. case 'image/jpeg':
41. $source_image = imagecreatefromjpeg($filepath);
42. break;
43. case 'image/png':
44. $source_image = imagecreatefrompng($filepath);
45. break;
46. default:
47. return false;
48. break;
49. }
50. $target_image = imagecreatetruecolor($new_width, $new_height);
51. $cropped_image = imagecreatetruecolor($cropped_width, $cropped_height);
52. // 裁剪
53. imagecopy($cropped_image, $source_image, 0, 0, $source_x, $source_y, $cropped_width, $cropped_height);
54. // 缩放
55. imagecopyresampled($target_image, $cropped_image, 0, 0, 0, 0, $new_width, $new_height, $cropped_width, $cropped_height);
56. header('Content-Type: image/jpeg');
57. imagejpeg($target_image);
58. imagedestroy($source_image);
59. imagedestroy($target_image);
60. imagedestroy($cropped_image);
61. }

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