How does PHP generate adaptive thumbnails?

Source: Internet
Author: User
Tags image identifier
How does PHP generate adaptive thumbnails?

Create a new file named thumbnailimage. php for the php class that generates thumbnails. it is best not to use uppercase letters for the file name.

  1. Define ('max _ IMG_SIZE ', 100000 );
  2. // Supported image types
  3. Define ('thumb _ JPEG ', 'image/jpeg ');
  4. Define ('thumb _ PNG ', 'image/png ');
  5. Define ('thumb _ GIF', 'image/GIF ');
  6. // Interlacing modes
  7. Define ('interlace _ off', 0 );
  8. Define ('interlace _ on', 1 );
  9. // Output modes
  10. Define ('stdout ','');
  11. // Empty constants
  12. Define ('no _ LOGO ','');
  13. Define ('no _ label ','');
  14. // Logo and label positioning
  15. Define ('Pos _ left', 0 );
  16. Define ('Pos _ right', 1 );
  17. Define ('Pos _ Center', 2 );
  18. Define ('Pos _ top', 3 );
  19. Define ('Pos _ BOTTOM ', 4 );
  20. // Error messages
  21. Define ('e _ 001', 'File% SDo not exist ');
  22. Define ('e _ 002', 'failed reading image data from% S');
  23. Define ('e _ 003 ', 'cannot create the copy% S');
  24. Define ('e _ 004 ', 'could not copy the logo image ');
  25. Define ('e _ 005 ', 'cannot create final image ');
  26. //************************************** **************************************
  27. // CLASS DEFINITION
  28. //************************************** **************************************
  29. Class ThumbnailImage
  30. {
  31. //************************************** **************************************
  32. // PUBLIC PROPERTIES
  33. //************************************** **************************************
  34. Var $ src_file; // source image file
  35. Var $ dest_file; // destination image file
  36. Var $ dest_type; // destination image type
  37. Var $ interlace; // destination image interlacing mode
  38. Var $ pai_quality; // quality of resulting JPEG
  39. Var $ max_width; // maximal thumbnail width
  40. Var $ max_height; // maximal thumbnail height
  41. Var $ fit_to_max; // enlarge small images?
  42. Var $ logo; // array of logo parameters
  43. Var $ label; // array of label parameters
  44. //************************************** **************************************
  45. // CLASS CONSTRUCTOR
  46. //************************************** **************************************
  47. /*
  48. Description:
  49. Defines default values for properties.
  50. Prototype:
  51. Void ThumbImg (string src_file = '')
  52. Parameters:
  53. Src_file-source image filename
  54. */
  55. Function ThumbnailImage ($ src_file = '')
  56. {
  57. $ This-> src_file = $ src_file;
  58. $ This-> dest_file = STDOUT;
  59. $ This-> dest_type = THUMB_JPEG;
  60. $ This-> interlace = INTERLACE_OFF;
  61. $ This-> pai_quality =-1;
  62. $ This-> max_width = 100;
  63. $ This-> max_height = 90;
  64. $ This-> fit_to_max = FALSE;
  65. $ This-> logo ['file'] = NO_LOGO;
  66. $ This-> logo ['vert _ Pos'] = POS_TOP;
  67. $ This-> logo ['horz _ Pos'] = POS_LEFT;
  68. $ This-> label ['text'] = NO_LABEL;
  69. $ This-> label ['vert _ Pos'] = POS_BOTTOM;
  70. $ This-> label ['horz _ Pos'] = POS_RIGHT;
  71. $ This-> label ['font'] = '';
  72. $ This-> label ['size'] = 20;
  73. $ This-> label ['color'] = '#000000 ';
  74. $ This-> label ['angle '] = 0;
  75. }
  76. //************************************** **************************************
  77. // PRIVATE METHODS
  78. //************************************** **************************************
  79. /*
  80. Description:
  81. Extracts decimal color components from hex color string.
  82. Prototype:
  83. Array ParseColor (string hex_color)
  84. Parameters:
  85. Hex_color-color in '# rrggbb' format
  86. Return:
  87. Decimal values for red, green and blue color components.
  88. */
  89. Function ParseColor ($ hex_color)
  90. {
  91. If (strpos ($ hex_color, '#') = 0)
  92. $ Hex_color = substr ($ hex_color, 1 );
  93. $ R = hexdec (substr ($ hex_color, 0, 2 ));
  94. $ G = hexdec (substr ($ hex_color, 2, 2 ));
  95. $ B = hexdec (substr ($ hex_color, 4, 2 ));
  96. Return array ($ r, $ g, $ B );
  97. }
  98. /*
  99. Description:
  100. Retrives image data as a string.
  101. Thanks to Luis Larrateguy for the idea of this function.
  102. Prototype:
  103. String GetImageStr (string image_file)
  104. Parameters:
  105. Image_file-filename of image
  106. Return:
  107. Image file contents string.
  108. */
  109. Function GetImageStr ($ image_file)
  110. {
  111. If (function_exists ('File _ get_contents '))
  112. {
  113. $ Str = @ file_get_contents ($ image_file );
  114. If (! $ Str)
  115. {
  116. $ Err = sprintf (E_002, $ image_file );
  117. Trigger_error ($ err, E_USER_ERROR );
  118. }
  119. Return $ str;
  120. }
  121. $ F = fopen ($ image_file, 'RB ');
  122. If (! $ F)
  123. {
  124. $ Err = sprintf (E_002, $ image_file );
  125. Trigger_error ($ err, E_USER_ERROR );
  126. }
  127. $ Fsz = @ filesize ($ image_file );
  128. If (! $ Fsz)
  129. $ Fsz = MAX_IMG_SIZE;
  130. $ Str = fread ($ f, $ fsz );
  131. Fclose ($ f );
  132. Return $ str;
  133. }
  134. /*
  135. Description:
  136. Loads image from file.
  137. Prototype:
  138. Resource LoadImage (string image_file, int & image_width, int & image_height)
  139. Parameters:
  140. Image_file-filename of image
  141. Image_width-width of loaded image
  142. Image_height-height of loaded image
  143. Return:
  144. Image identifier representing the image obtained from the given file.
  145. */
  146. Function LoadImage ($ image_file, & $ image_width, & $ image_height)
  147. {
  148. $ Image_width = 0;
  149. $ Image_height = 0;
  150. $ Image_data = $ this-> GetImageStr ($ image_file );
  151. $ Image = imagecreatefromstring ($ image_data );
  152. If (! $ Image)
  153. {
  154. $ Err = sprintf (E_003, $ image_file );
  155. Trigger_error ($ err, E_USER_ERROR );
  156. }
  157. $ Image_width = imagesx ($ image );
  158. $ Image_height = imagesy ($ image );
  159. Return $ image;
  160. }
  161. /*
  162. Description:
  163. Calculates thumbnail image sizes from source image width and height.
  164. Prototype:
  165. Array GetThumbSize (int src_width, int src_height)
  166. Parameters:
  167. Src_width-width of source image
  168. Src_height-height of source image
  169. Return:
  170. An array with 2 elements. Index 0 contains the width of thumbnail image
  171. And index 1 contains the height.
  172. */Generate a thumbnail
  173. Function GetThumbSize ($ src_width, $ src_height)
  174. {
  175. $ Max_width = $ this-> max_width;
  176. $ Max_height = $ this-> max_height;
  177. $ X_ratio = $ max_width/$ src_width;
  178. $ Y_ratio = $ max_height/$ src_height;
  179. $ Is_small = ($ src_width <= $ max_width & $ src_height <= $ max_height );
  180. If (! $ This-> fit_to_max & $ is_small)
  181. {
  182. $ Dest_width = $ src_width;
  183. $ Dest_height = $ src_height;
  184. }
  185. Elseif ($ x_ratio * $ src_height <$ max_height)
  186. {
  187. $ Dest_width = $ max_width;
  188. $ Dest_height = ceil ($ x_ratio * $ src_height );
  189. }
  190. Else
  191. {
  192. $ Dest_width = ceil ($ y_ratio * $ src_width );
  193. $ Dest_height = $ max_height;
  194. }
  195. Return array ($ dest_width, $ dest_height );
  196. }
  197. /*
  198. Description:
  199. Adds logo image to thumbnail.
  200. Prototype:
  201. Void AddLogo (int thumb_width, int thumb_height, resource & thumb_img)
  202. Parameters:
  203. Thumb_width-width of thumbnail image
  204. Thumb_height-height of thumbnail image
  205. Thumb_img-thumbnail image identifier
  206. */
  207. Function AddLogo ($ thumb_width, $ thumb_height, & $ thumb_img)
  208. {
  209. Extract ($ this-> logo );
  210. $ Logo_image = $ this-> LoadImage ($ file, $ logo_width, $ logo_height );
  211. If ($ vert_pos = POS_CENTER)
  212. $ Y_pos = ceil ($ thumb_height/2-$ logo_height/2 );
  213. Elseif ($ vert_pos = POS_BOTTOM)
  214. $ Y_pos = $ thumb_height-$ logo_height;
  215. Else
  216. $ Y_pos = 0;
  217. If ($ horz_pos = POS_CENTER)
  218. $ X_pos = ceil ($ thumb_width/2-$ logo_width/2 );
  219. Elseif ($ horz_pos = POS_RIGHT)
  220. $ X_pos = $ thumb_width-$ logo_width;
  221. Else
  222. $ X_pos = 0;
  223. If (! Imagecopy ($ thumb_img, $ logo_image, $ x_pos, $ y_pos, 0, 0,
  224. $ Logo_width, $ logo_height ))
  225. Trigger_error (E_004, E_USER_ERROR );
  226. }
  227. /*
  228. Description:
  229. Adds label text to thumbnail.
  230. Prototype:
  231. Void AddLabel (int thumb_width, int thumb_height, resource & thumb_img)
  232. Parameters:
  233. Thumb_width-width of thumbnail image
  234. Thumb_height-height of thumbnail image
  235. Thumb_img-thumbnail image identifier
  236. */
  237. Function AddLabel ($ thumb_width, $ thumb_height, & $ thumb_img)
  238. {
  239. Extract ($ this-> label );
  240. List ($ r, $ g, $ B) = $ this-> ParseColor ($ color );
  241. $ Color_id = imagecolorallocate ($ thumb_img, $ r, $ g, $ B );
  242. $ Text_box = imagettfbbox ($ size, $ angle, $ font, $ text );
  243. $ Text_width = $ text_box [2]-$ text_box [0];
  244. $ Text_height = abs ($ text_box [1]-$ text_box [7]);
  245. If ($ vert_pos = POS_TOP)
  246. $ Y_pos = 5 + $ text_height;
  247. Elseif ($ vert_pos = POS_CENTER)
  248. $ Y_pos = ceil ($ thumb_height/2-$ text_height/2 );
  249. Elseif ($ vert_pos = POS_BOTTOM)
  250. $ Y_pos = $ thumb_height-$ text_height;
  251. If ($ horz_pos = POS_LEFT)
  252. $ X_pos = 5;
  253. Elseif ($ horz_pos = POS_CENTER)
  254. $ X_pos = ceil ($ thumb_width/2-$ text_width/2 );
  255. Elseif ($ horz_pos = POS_RIGHT)
  256. $ X_pos = $ thumb_width-$ text_width-5;
  257. Imagettftext ($ thumb_img, $ size, $ angle, $ x_pos, $ y_pos,
  258. $ Color_id, $ font, $ text );
  259. }
  260. /*
  261. Description:
  262. Output thumbnail image into the browser.
  263. Prototype:
  264. Void OutputThumbImage (resource dest_image)
  265. Parameters:
  266. Dest_img-thumbnail image identifier
  267. */Output thumbnails
  268. Function OutputThumbImage ($ dest_image)
  269. {
  270. Imageinterlace ($ dest_image, $ this-> interlace );
  271. Header ('content-type: '. $ this-> dest_type );
  272. If ($ this-> dest_type = THUMB_JPEG)
  273. Imagejpeg ($ dest_image, '', $ this-> pai_quality );
  274. Elseif ($ this-> dest_type = THUMB_GIF)
  275. Imagegif ($ dest_image );
  276. Elseif ($ this-> dest_type = THUMB_PNG)
  277. Imagepng ($ dest_image );
  278. }
  279. /*
  280. Description:
  281. Save thumbnail image into the disc file.
  282. Prototype:
  283. Void SaveThumbImage (string image_file, resource dest_image)
  284. Parameters:
  285. Image_file-destination file name
  286. Dest_img-thumbnail image identifier
  287. */
  288. Function SaveThumbImage ($ image_file, $ dest_image)
  289. {
  290. Imageinterlace ($ dest_image, $ this-> interlace );
  291. If ($ this-> dest_type = THUMB_JPEG)
  292. Imagejpeg ($ dest_image, $ this-> dest_file, $ this-> pai_quality );
  293. Elseif ($ this-> dest_type = THUMB_GIF)
  294. Imagegif ($ dest_image, $ this-> dest_file );
  295. Elseif ($ this-> dest_type = THUMB_PNG)
  296. Imagepng ($ dest_image, $ this-> dest_file );
  297. }
  298. //************************************** **************************************
  299. // PUBLIC METHODS
  300. //************************************** **************************************
  301. /*
  302. Description:
  303. Output thumbnail image into the browser or disc file according to
  304. Values of parameters.
  305. Prototype:
  306. Void Output ()
  307. */Generate a thumbnail.
  308. Function Output ()
  309. {
  310. $ Src_image = $ this-> LoadImage ($ this-> src_file, $ src_width, $ src_height );
  311. $ Dest_size = $ this-> GetThumbSize ($ src_width, $ src_height );
  312. $ Dest_width = $ dest_size [0];
  313. $ Dest_height = $ dest_size [1];
  314. $ Dest_image = imagecreatetruecolor ($ dest_width, $ dest_height );
  315. If (! $ Dest_image)
  316. Trigger_error (E_005, E_USER_ERROR );
  317. Imagecopyresampled ($ dest_image, $ src_image, 0, 0, 0, 0,
  318. $ Dest_width, $ dest_height, $ src_width, $ src_height );
  319. If ($ this-> logo ['file']! = NO_LOGO)
  320. $ This-> AddLogo ($ dest_width, $ dest_height, $ dest_image );
  321. If ($ this-> label ['text']! = NO_LABEL)
  322. $ This-> AddLabel ($ dest_width, $ dest_height, $ dest_image );
  323. If ($ this-> dest_file = STDOUT)
  324. $ This-> OutputThumbImage ($ dest_image );
  325. Else
  326. $ This-> SaveThumbImage ($ this-> dest_file, $ dest_image );
  327. Imagedestroy ($ src_image );
  328. Imagedestroy ($ dest_image );
  329. }
  330. } // End of class definition
  331. ?>

Usage: 1. first reference the php file (do not tell me) 2. call the code

  1. $ Tis = new ThumbnailImage ();
  2. $ Tis-> src_file = "path of the source file written here"
  3. $ Tis-> dest_type = THUMB_JPEG; // The image generation type is jpg.
  4. $ Tis-> dest_file = 'write the path of the destination file ';
  5. $ Tis-> max_width = 120; // adaptive size, but the maximum width is 120
  6. $ Tis-> max_height = 4000; // adaptive size, but the maximum height is 4000
  7. $ Tis-> Output ();

The key to the code is: max_width and max_height. generally, thumbnails are generated very well unless the images are personalized.

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