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PHP实现对png图像进行缩放的方法(支持透明背景)

时间:2021-07-01 10:21:17 帮助过:28人阅读

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。

PHP, png

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