这篇文章主要介绍了PHP实现对png图像进行缩放的方法(支持透明背景),可实现php针对png图像的缩放功能,且支持透明背景,具有一定参考借鉴价值,需要的朋友可以参考下。

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：

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

希望本文所述对大家的php程序设计有所帮助。