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

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希望本文所述对大家的php程序设计有所帮助。

PHP, png