How does PHP generate adaptive thumbnails?

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. Define ('max _ IMG_SIZE ', 100000 ); // Supported image types Define ('thumb _ JPEG ', 'image/jpeg '); Define ('thumb _ PNG ', 'image/png '); Define ('thumb _ GIF', 'image/GIF '); // Interlacing modes Define ('interlace _ off', 0 ); Define ('interlace _ on', 1 ); // Output modes Define ('stdout ',''); // Empty constants Define ('no _ LOGO ',''); Define ('no _ label ',''); // Logo and label positioning Define ('Pos _ left', 0 ); Define ('Pos _ right', 1 ); Define ('Pos _ Center', 2 ); Define ('Pos _ top', 3 ); Define ('Pos _ BOTTOM ', 4 ); // Error messages Define ('e _ 001', 'File% SDo not exist '); Define ('e _ 002', 'failed reading image data from% S'); Define ('e _ 003 ', 'cannot create the copy% S'); Define ('e _ 004 ', 'could not copy the logo image '); Define ('e _ 005 ', 'cannot create final image '); //************************************** ************************************** // CLASS DEFINITION //************************************** ************************************** Class ThumbnailImage { //************************************** ************************************** // PUBLIC PROPERTIES //************************************** ************************************** Var $ src_file; // source image file Var $ dest_file; // destination image file Var $ dest_type; // destination image type Var $ interlace; // destination image interlacing mode Var $ pai_quality; // quality of resulting JPEG Var $ max_width; // maximal thumbnail width Var $ max_height; // maximal thumbnail height Var $ fit_to_max; // enlarge small images? Var $ logo; // array of logo parameters Var $ label; // array of label parameters //************************************** ************************************** // CLASS CONSTRUCTOR //************************************** ************************************** /* Description: Defines default values for properties. Prototype: Void ThumbImg (string src_file = '') Parameters: Src_file-source image filename */ Function ThumbnailImage ($ src_file = '') { $ This-> src_file = $ src_file; $ This-> dest_file = STDOUT; $ This-> dest_type = THUMB_JPEG; $ This-> interlace = INTERLACE_OFF; $ This-> pai_quality =-1; $ This-> max_width = 100; $ This-> max_height = 90; $ This-> fit_to_max = FALSE; $ This-> logo ['file'] = NO_LOGO; $ This-> logo ['vert _ Pos'] = POS_TOP; $ This-> logo ['horz _ Pos'] = POS_LEFT; $ This-> label ['text'] = NO_LABEL; $ This-> label ['vert _ Pos'] = POS_BOTTOM; $ This-> label ['horz _ Pos'] = POS_RIGHT; $ This-> label ['font'] = ''; $ This-> label ['size'] = 20; $ This-> label ['color'] = '#000000 '; $ This-> label ['angle '] = 0; } //************************************** ************************************** // PRIVATE METHODS //************************************** ************************************** /* Description: Extracts decimal color components from hex color string. Prototype: Array ParseColor (string hex_color) Parameters: Hex_color-color in '# rrggbb' format Return: Decimal values for red, green and blue color components. */ Function ParseColor ($ hex_color) { If (strpos ($ hex_color, '#') = 0) $ Hex_color = substr ($ hex_color, 1 ); $ R = hexdec (substr ($ hex_color, 0, 2 )); $ G = hexdec (substr ($ hex_color, 2, 2 )); $ B = hexdec (substr ($ hex_color, 4, 2 )); Return array ($ r, $ g, $ B ); } /* Description: Retrives image data as a string. Thanks to Luis Larrateguy for the idea of this function. Prototype: String GetImageStr (string image_file) Parameters: Image_file-filename of image Return: Image file contents string. */ Function GetImageStr ($ image_file) { If (function_exists ('File _ get_contents ')) { $ Str = @ file_get_contents ($ image_file ); If (! $ Str) { $ Err = sprintf (E_002, $ image_file ); Trigger_error ($ err, E_USER_ERROR ); } Return $ str; } $ F = fopen ($ image_file, 'RB '); If (! $ F) { $ Err = sprintf (E_002, $ image_file ); Trigger_error ($ err, E_USER_ERROR ); } $ Fsz = @ filesize ($ image_file ); If (! $ Fsz) $ Fsz = MAX_IMG_SIZE; $ Str = fread ($ f, $ fsz ); Fclose ($ f ); Return $ str; } /* Description: Loads image from file. Prototype: Resource LoadImage (string image_file, int & image_width, int & image_height) Parameters: Image_file-filename of image Image_width-width of loaded image Image_height-height of loaded image Return: Image identifier representing the image obtained from the given file. */ Function LoadImage ($ image_file, & $ image_width, & $ image_height) { $ Image_width = 0; $ Image_height = 0; $ Image_data = $ this-> GetImageStr ($ image_file ); $ Image = imagecreatefromstring ($ image_data ); If (! $ Image) { $ Err = sprintf (E_003, $ image_file ); Trigger_error ($ err, E_USER_ERROR ); } $ Image_width = imagesx ($ image ); $ Image_height = imagesy ($ image ); Return $ image; } /* Description: Calculates thumbnail image sizes from source image width and height. Prototype: Array GetThumbSize (int src_width, int src_height) Parameters: Src_width-width of source image Src_height-height of source image Return: An array with 2 elements. Index 0 contains the width of thumbnail image And index 1 contains the height. */Generate a thumbnail Function GetThumbSize ($ src_width, $ src_height) { $ Max_width = $ this-> max_width; $ Max_height = $ this-> max_height; $ X_ratio = $ max_width/$ src_width; $ Y_ratio = $ max_height/$ src_height; $ Is_small = ($ src_width <= $ max_width & $ src_height <= $ max_height ); If (! $ This-> fit_to_max & $ is_small) { $ Dest_width = $ src_width; $ Dest_height = $ src_height; } Elseif ($ x_ratio * $ src_height <$ max_height) { $ Dest_width = $ max_width; $ Dest_height = ceil ($ x_ratio * $ src_height ); } Else { $ Dest_width = ceil ($ y_ratio * $ src_width ); $ Dest_height = $ max_height; } Return array ($ dest_width, $ dest_height ); } /* Description: Adds logo image to thumbnail. Prototype: Void AddLogo (int thumb_width, int thumb_height, resource & thumb_img) Parameters: Thumb_width-width of thumbnail image Thumb_height-height of thumbnail image Thumb_img-thumbnail image identifier */ Function AddLogo ($ thumb_width, $ thumb_height, & $ thumb_img) { Extract ($ this-> logo ); $ Logo_image = $ this-> LoadImage ($ file, $ logo_width, $ logo_height ); If ($ vert_pos = POS_CENTER) $ Y_pos = ceil ($ thumb_height/2-$ logo_height/2 ); Elseif ($ vert_pos = POS_BOTTOM) $ Y_pos = $ thumb_height-$ logo_height; Else $ Y_pos = 0; If ($ horz_pos = POS_CENTER) $ X_pos = ceil ($ thumb_width/2-$ logo_width/2 ); Elseif ($ horz_pos = POS_RIGHT) $ X_pos = $ thumb_width-$ logo_width; Else $ X_pos = 0; If (! Imagecopy ($ thumb_img, $ logo_image, $ x_pos, $ y_pos, 0, 0, $ Logo_width, $ logo_height )) Trigger_error (E_004, E_USER_ERROR ); } /* Description: Adds label text to thumbnail. Prototype: Void AddLabel (int thumb_width, int thumb_height, resource & thumb_img) Parameters: Thumb_width-width of thumbnail image Thumb_height-height of thumbnail image Thumb_img-thumbnail image identifier */ Function AddLabel ($ thumb_width, $ thumb_height, & $ thumb_img) { Extract ($ this-> label ); List ($ r, $ g, $ B) = $ this-> ParseColor ($ color ); $ Color_id = imagecolorallocate ($ thumb_img, $ r, $ g, $ B ); $ Text_box = imagettfbbox ($ size, $ angle, $ font, $ text ); $ Text_width = $ text_box [2]-$ text_box [0]; $ Text_height = abs ($ text_box [1]-$ text_box [7]); If ($ vert_pos = POS_TOP) $ Y_pos = 5 + $ text_height; Elseif ($ vert_pos = POS_CENTER) $ Y_pos = ceil ($ thumb_height/2-$ text_height/2 ); Elseif ($ vert_pos = POS_BOTTOM) $ Y_pos = $ thumb_height-$ text_height; If ($ horz_pos = POS_LEFT) $ X_pos = 5; Elseif ($ horz_pos = POS_CENTER) $ X_pos = ceil ($ thumb_width/2-$ text_width/2 ); Elseif ($ horz_pos = POS_RIGHT) $ X_pos = $ thumb_width-$ text_width-5; Imagettftext ($ thumb_img, $ size, $ angle, $ x_pos, $ y_pos, $ Color_id, $ font, $ text ); } /* Description: Output thumbnail image into the browser. Prototype: Void OutputThumbImage (resource dest_image) Parameters: Dest_img-thumbnail image identifier */Output thumbnails Function OutputThumbImage ($ dest_image) { Imageinterlace ($ dest_image, $ this-> interlace ); Header ('content-type: '. $ this-> dest_type ); If ($ this-> dest_type = THUMB_JPEG) Imagejpeg ($ dest_image, '', $ this-> pai_quality ); Elseif ($ this-> dest_type = THUMB_GIF) Imagegif ($ dest_image ); Elseif ($ this-> dest_type = THUMB_PNG) Imagepng ($ dest_image ); } /* Description: Save thumbnail image into the disc file. Prototype: Void SaveThumbImage (string image_file, resource dest_image) Parameters: Image_file-destination file name Dest_img-thumbnail image identifier */ Function SaveThumbImage ($ image_file, $ dest_image) { Imageinterlace ($ dest_image, $ this-> interlace ); If ($ this-> dest_type = THUMB_JPEG) Imagejpeg ($ dest_image, $ this-> dest_file, $ this-> pai_quality ); Elseif ($ this-> dest_type = THUMB_GIF) Imagegif ($ dest_image, $ this-> dest_file ); Elseif ($ this-> dest_type = THUMB_PNG) Imagepng ($ dest_image, $ this-> dest_file ); } //************************************** ************************************** // PUBLIC METHODS //************************************** ************************************** /* Description: Output thumbnail image into the browser or disc file according to Values of parameters. Prototype: Void Output () */Generate a thumbnail. Function Output () { $ Src_image = $ this-> LoadImage ($ this-> src_file, $ src_width, $ src_height ); $ Dest_size = $ this-> GetThumbSize ($ src_width, $ src_height ); $ Dest_width = $ dest_size [0]; $ Dest_height = $ dest_size [1]; $ Dest_image = imagecreatetruecolor ($ dest_width, $ dest_height ); If (! $ Dest_image) Trigger_error (E_005, E_USER_ERROR ); Imagecopyresampled ($ dest_image, $ src_image, 0, 0, 0, 0, $ Dest_width, $ dest_height, $ src_width, $ src_height ); If ($ this-> logo ['file']! = NO_LOGO) $ This-> AddLogo ($ dest_width, $ dest_height, $ dest_image ); If ($ this-> label ['text']! = NO_LABEL) $ This-> AddLabel ($ dest_width, $ dest_height, $ dest_image ); If ($ this-> dest_file = STDOUT) $ This-> OutputThumbImage ($ dest_image ); Else $ This-> SaveThumbImage ($ this-> dest_file, $ dest_image ); Imagedestroy ($ src_image ); Imagedestroy ($ dest_image ); } } // End of class definition ?> Usage: 1. first reference the php file (do not tell me) 2. call the code $ Tis = new ThumbnailImage (); $ Tis-> src_file = "path of the source file written here" $ Tis-> dest_type = THUMB_JPEG; // The image generation type is jpg. $ Tis-> dest_file = 'write the path of the destination file '; $ Tis-> max_width = 120; // adaptive size, but the maximum width is 120 $ Tis-> max_height = 4000; // adaptive size, but the maximum height is 4000 $ Tis-> Output (); The key to the code is: max_width and max_height. generally, thumbnails are generated very well unless the images are personalized.