PHP实现对png图像进行缩放的方法(支持透明背景)

本文实例讲述了PHP实现对png图像进行缩放的方法。分享给大家供大家参考。具体实现方法如下：

2. function smart_resize_image( $file, $width = 0, $height = 0, $proportional = false, $output = 'file', $delete_original = true, $use_linux_commands = false )
3. {
4. if ( $height <= 0 && $width <= 0 ) {
5. return false;
6. }
7. $info = getimagesize($file);
8. $image = '';
9. $final_width = 0;
10. $final_height = 0;
11. list($width_old, $height_old) = $info;
12. if ($proportional) {
13. if ($width == 0) $factor = $height/$height_old;
14. elseif ($height == 0) $factor = $width/$width_old;
15. else $factor = min ( $width / $width_old, $height / $height_old);
16. $final_width = round ($width_old * $factor);
17. $final_height = round ($height_old * $factor);
18. }
19. else {
20. $final_width = ( $width <= 0 ) ? $width_old : $width;
21. $final_height = ( $height <= 0 ) ? $height_old : $height;
22. }
23. switch ($info[2] ) {
24. case IMAGETYPE_GIF:
25. $image = imagecreatefromgif($file);
26. break;
27. case IMAGETYPE_JPEG:
28. $image = imagecreatefromjpeg($file);
29. break;
30. case IMAGETYPE_PNG:
31. $image = imagecreatefrompng($file);
32. break;
33. default:
34. return false;
35. }
36. $image_resized = imagecreatetruecolor( $final_width, $final_height );
37. if ( ($info[2] == IMAGETYPE_GIF) || ($info[2] == IMAGETYPE_PNG) ) {
38. $trnprt_indx = imagecolortransparent($image);
39. // If we have a specific transparent color
40. if ($trnprt_indx >= 0) {
41. // Get the original image's transparent color's RGB values
42. $trnprt_color = imagecolorsforindex($image, $trnprt_indx);
43. // Allocate the same color in the new image resource
44. $trnprt_indx = imagecolorallocate($image_resized, $trnprt_color['red'], $trnprt_color['green'], $trnprt_color['blue']);
45. // Completely fill the background of the new image with allocated color.
46. imagefill($image_resized, 0, 0, $trnprt_indx);
47. // Set the background color for new image to transparent
48. imagecolortransparent($image_resized, $trnprt_indx);
49. }
50. // Always make a transparent background color for PNGs that don't have one allocated already
51. elseif ($info[2] == IMAGETYPE_PNG) {
52. // Turn off transparency blending (temporarily)
53. imagealphablending($image_resized, false);
54. // Create a new transparent color for image
55. $color = imagecolorallocatealpha($image_resized, 0, 0, 0, 127);
56. // Completely fill the background of the new image with allocated color.
57. imagefill($image_resized, 0, 0, $color);
58. // Restore transparency blending
59. imagesavealpha($image_resized, true);
60. }
61. }
62. imagecopyresampled($image_resized, $image, 0, 0, 0, 0, $final_width, $final_height, $width_old, $height_old);
63. if ( $delete_original ) {
64. if ( $use_linux_commands )
65. exec('rm '.$file);
66. else
67. @unlink($file);
68. }
69. switch ( strtolower($output) ) {
70. case 'browser':
71. $mime = image_type_to_mime_type($info[2]);
72. header("Content-type: $mime");
73. $output = NULL;
74. break;
75. case 'file':
76. $output = $file;
77. break;
78. case 'return':
79. return $image_resized;
80. break;
81. default:
82. break;
83. }
84. switch ($info[2] ) {
85. case IMAGETYPE_GIF:
86. imagegif($image_resized, $output);
87. break;
88. case IMAGETYPE_JPEG:
89. imagejpeg($image_resized, $output);
90. break;
91. case IMAGETYPE_PNG:
92. imagepng($image_resized, $output);
93. break;
94. default:
95. return false;
96. }
97. return true;
98. }

希望本文所述对大家的php程序设计有所帮助。