PHP implements a method for zooming a PNG image (supports transparent backgrounds)

Source: Internet
Author: User
Tags transparent color

The example in this paper describes how PHP implements scaling of PNG images. Share to everyone for your reference. The implementation method is as follows:

  1. function Smart_resize_image ($file, $width = 0, $height = 0, $proportional = false, $output = ' file ', $delete _original = t Rue, $use _linux_commands = False)
  2. {
  3. if ($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, $trnprt _indx);
  48. }
  49. Always make a transparent background color for PNGs that don ' t has one allocated already
  50. ElseIf ($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. }
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I hope this article is helpful to everyone's PHP programming.

PHP, PNG
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