PHP生成自适应大小的缩略图类及使用方法分享

<?php

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 <b>%s</b> do not exist' );
define ( 'e_002', 'failed reading image data from <b>%s</b>' );
define ( 'e_003', 'cannot create the copy of <b>%s</b>' );
define ( 'e_004', 'cannot 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 $jpeg_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->jpeg_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.
  */
  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
  */
  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->jpeg_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->jpeg_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 the
      values of parameters.
    prototype:
      void output ( )
  */
  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

?>

 $tis = new thumbnailimage();
     $tis->src_file  = "这里写源文件的路径"
     $tis->dest_type = thumb_jpeg;//生成图片的类型是 jpg
      $tis->dest_file = '这里写目标文件的路径';

     $tis->max_width = 120;//自适应大小，但是最大宽度为120
     $tis->max_height = 4000; //自适应大小，但是最大高度为4000
     $tis->output();