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PHP如何生成自适应大小的缩略图

时间:2021-07-01 10:21:17 帮助过:23人阅读

生成缩略图的php类,新建一个文件叫做 thumbnailimage.php,文件名最好不要用大写。

  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 %s do not exist' );
  22. define ( 'E_002', 'Failed reading image data from %s' );
  23. define ( 'E_003', 'Cannot create the copy of %s' );
  24. define ( 'E_004', 'Cannot 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 $jpeg_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->jpeg_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. */ 生成缩略图
  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. */ 输出缩略图
  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->jpeg_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->jpeg_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 the
  304. values of parameters.
  305. Prototype:
  306. void Output ( )
  307. */ 生成缩略图片
  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. ?>

使用方法: 1、首先引用该php文件(不要告诉我不会) 2、调用代码

  1. $tis = new ThumbnailImage();
  2. $tis->src_file = "这里写源文件的路径"
  3. $tis->dest_type = THUMB_JPEG;//生成图片的类型是 jpg
  4. $tis->dest_file = '这里写目标文件的路径';
  5. $tis->max_width = 120;//自适应大小,但是最大宽度为120
  6. $tis->max_height = 4000; //自适应大小,但是最大高度为4000
  7. $tis->Output();

代码关键在于: max_width 和max_height, 一般来说除非图片很有个性,否则缩略图生成的还是很不错的。

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