Club Drupal

<?php

/**

 * @file

 * Functions for the generation of the CAPTCHA image.

 *

 * Loosely Based on MyCaptcha by Heine Deelstra

 * (http://heine.familiedeelstra.com/mycaptcha-download)

 */

/**

 * Menu callback function that generates the CAPTCHA image.

 */

function image_captcha_image() {

  // If output buffering is on: discard current content and disable further buffering.

  if (ob_get_level()) {

    ob_end_clean();

  }

  if (!isset($_GET['sid']) || is_array($_GET['sid'])) {

    exit();

  }

  $captcha_sid = $_GET['sid'];

  // Get solution (the code to show).

  $code = db_query("SELECT solution FROM {captcha_sessions} WHERE csid = :csid",

    array(':csid' => $captcha_sid)

  )->fetchField();

  // Only generate captcha if code exists in the session.

  if ($code !== FALSE) {

    // Seed the random generators used for image CAPTCHA distortion based on session and code

    // to counter attacks that re-request the same challenge and pick the simplest image one or combine info.

    $seed = (int) hexdec(substr(md5($captcha_sid . $code), 0, 8));

    srand($seed);

    mt_srand($seed);

    // Generate the image.

    $image = @_image_captcha_generate_image($code);

    // Check of generation was successful.

    if (!$image) {

      watchdog('CAPTCHA', 'Generation of image CAPTCHA failed. Check your image CAPTCHA configuration and especially the used font.', array(), WATCHDOG_ERROR);

      exit();

    }

    // Send the image resource as an image file to the client.

    $file_format = variable_get('image_captcha_file_format', IMAGE_CAPTCHA_FILE_FORMAT_JPG);

    if ($file_format == IMAGE_CAPTCHA_FILE_FORMAT_JPG) {

      drupal_add_http_header('Content-Type', 'image/jpeg');

      imagejpeg($image);

    }

    else {

      drupal_add_http_header('Content-Type', 'image/png');

      imagepng($image);

    }

    // Clean up the image resource.

    imagedestroy($image);

  }

  exit();

}

/**

 * Small helper function for parsing a hexadecimal color to a RGB tuple.

 */

function _image_captcha_hex_to_rgb($hex) {

  // Handle #RGB format/

  if (strlen($hex) == 4) {

    $hex = $hex[1] . $hex[1] . $hex[2] . $hex[2] . $hex[3] . $hex[3];

  }

  $c = hexdec($hex);

  $rgb = array();

  for ($i = 16; $i >= 0; $i -= 8) {

    $rgb[] = ($c >> $i) & 0xFF;

  }

  return $rgb;

}

/**

 * Base function for generating a image CAPTCHA.

 */

function _image_captcha_generate_image($code) {

  // Get font.

  $fonts = _image_captcha_get_enabled_fonts();

  // Get other settings.

  $font_size = (int) variable_get('image_captcha_font_size', 30);

  list($width, $height) = _image_captcha_image_size($code);

  // Create image resource.

  $image = imagecreatetruecolor($width, $height);

  if (!$image) {

    return FALSE;

  }

  // Get the background color and paint the background.

  $background_rgb = _image_captcha_hex_to_rgb(variable_get('image_captcha_background_color', '#ffffff'));

  $background_color = imagecolorallocate($image, $background_rgb[0], $background_rgb[1], $background_rgb[2]);

  // Set transparency if needed.

  $file_format = variable_get('image_captcha_file_format', IMAGE_CAPTCHA_FILE_FORMAT_JPG);

  if ($file_format == IMAGE_CAPTCHA_FILE_FORMAT_TRANSPARENT_PNG) {

    imagecolortransparent($image, $background_color);

  }

  imagefilledrectangle($image, 0, 0, $width, $height, $background_color);

  // Do we need to draw in RTL mode?

  global $language;

  $rtl = $language->direction && ((bool) variable_get('image_captcha_rtl_support', 0));

  // Draw text.

  $result = _image_captcha_image_generator_print_string($image, $width, $height, $fonts, $font_size, $code, $rtl);

  if (!$result) {

    return FALSE;

  }

  // Add noise.

  $noise_colors = array();

  for ($i = 0; $i < 20; $i++) {

    $noise_colors[] = imagecolorallocate($image, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));

  }

  // Add additional noise.

  if (variable_get('image_captcha_dot_noise', 0)) {

    _image_captcha_image_generator_add_dots($image, $width, $height, $noise_colors);

  }

  if (variable_get('image_captcha_line_noise', 0)) {

    _image_captcha_image_generator_add_lines($image, $width, $height, $noise_colors);

  }

  // Distort the image.

  $distortion_amplitude = .25 * $font_size * variable_get('image_captcha_distortion_amplitude', 0) / 10.0;

  if ($distortion_amplitude > 1) {

    // Distortion parameters.

    $wavelength_xr = (2 + 3 * mt_rand(0, 1000) / 1000) * $font_size;

    $wavelength_yr = (2 + 3 * mt_rand(0, 1000) / 1000) * $font_size;

    $freq_xr = 2 * 3.141592 / $wavelength_xr;

    $freq_yr = 2 * 3.141592 / $wavelength_yr;

    $wavelength_xt = (2 + 3 * mt_rand(0, 1000) / 1000) * $font_size;

    $wavelength_yt = (2 + 3 * mt_rand(0, 1000) / 1000) * $font_size;

    $freq_xt = 2 * 3.141592 / $wavelength_xt;

    $freq_yt = 2 * 3.141592 / $wavelength_yt;

    $distorted_image = imagecreatetruecolor($width, $height);

    if ($file_format == IMAGE_CAPTCHA_FILE_FORMAT_TRANSPARENT_PNG) {

      imagecolortransparent($distorted_image, $background_color);

    }

    if (!$distorted_image) {

      return FALSE;

    }

    if (variable_get('image_captcha_bilinear_interpolation', FALSE)) {

      // Distortion with bilinear interpolation.

      for ($x = 0; $x < $width; $x++) {

        for ($y = 0; $y < $height; $y++) {

          // Get distorted sample point in source image.

          $r = $distortion_amplitude * sin($x * $freq_xr + $y * $freq_yr);

          $theta = $x * $freq_xt + $y * $freq_yt;

          $sx = $x + $r * cos($theta);

          $sy = $y + $r * sin($theta);

          $sxf = (int) floor($sx);

          $syf = (int) floor($sy);

          if ($sxf < 0 || $syf < 0 || $sxf >= $width - 1 || $syf >= $height - 1) {

            $color = $background_color;

          }

          else {

            // Bilinear interpolation: sample at four corners.

            $color_00 = imagecolorat($image, $sxf, $syf);

            $color_00_r = ($color_00 >> 16) & 0xFF;

            $color_00_g = ($color_00 >> 8) & 0xFF;

            $color_00_b = $color_00 & 0xFF;

            $color_10 = imagecolorat($image, $sxf + 1, $syf);

            $color_10_r = ($color_10 >> 16) & 0xFF;

            $color_10_g = ($color_10 >> 8) & 0xFF;

            $color_10_b = $color_10 & 0xFF;

            $color_01 = imagecolorat($image, $sxf, $syf + 1);

            $color_01_r = ($color_01 >> 16) & 0xFF;

            $color_01_g = ($color_01 >> 8) & 0xFF;

            $color_01_b = $color_01 & 0xFF;

            $color_11 = imagecolorat($image, $sxf + 1, $syf + 1);

            $color_11_r = ($color_11 >> 16) & 0xFF;

            $color_11_g = ($color_11 >> 8) & 0xFF;

            $color_11_b = $color_11 & 0xFF;

            // Interpolation factors.

            $u  = $sx - $sxf;

            $v  = $sy - $syf;

            // Interpolate.

            $r = (int) ((1 - $v) * ((1 - $u) * $color_00_r + $u * $color_10_r) + $v * ((1 - $u) * $color_01_r + $u * $color_11_r));

            $g = (int) ((1 - $v) * ((1 - $u) * $color_00_g + $u * $color_10_g) + $v * ((1 - $u) * $color_01_g + $u * $color_11_g));

            $b = (int) ((1 - $v) * ((1 - $u) * $color_00_b + $u * $color_10_b) + $v * ((1 - $u) * $color_01_b + $u * $color_11_b));

            // Build color.

            $color = ($r<<16) + ($g<<8) + $b;

          }

          imagesetpixel($distorted_image, $x, $y, $color);

        }

      }

    }

    else {

      // Distortion with nearest neighbor interpolation.

      for ($x = 0; $x < $width; $x++) {

        for ($y = 0; $y < $height; $y++) {

          // Get distorted sample point in source image.

          $r = $distortion_amplitude * sin($x * $freq_xr + $y * $freq_yr);

          $theta = $x * $freq_xt + $y * $freq_yt;

          $sx = $x + $r * cos($theta);

          $sy = $y + $r * sin($theta);

          $sxf = (int) floor($sx);

          $syf = (int) floor($sy);

          if ($sxf < 0 || $syf < 0 || $sxf >= $width - 1 || $syf >= $height - 1) {

            $color = $background_color;

          }

          else {

            $color = imagecolorat($image, $sxf, $syf);

          }

          imagesetpixel($distorted_image, $x, $y, $color);

        }

      }

    }

    // Release undistorted image.

    imagedestroy($image);

    // Return distorted image.

    return $distorted_image;

  }

  else {

    return $image;

  }

}

/**

 * Add lines.

 */

function _image_captcha_image_generator_add_lines(&$image, $width, $height, $colors) {

  $line_quantity = $width * $height / 200.0 * ((int) variable_get('image_captcha_noise_level', 5)) / 10.0;

  for ($i = 0; $i < $line_quantity; $i++) {

    imageline($image, mt_rand(0, $width), mt_rand(0, $height), mt_rand(0, $width), mt_rand(0, $height), $colors[array_rand($colors)]);

  }

}

/**

 * Add dots.

 */

function _image_captcha_image_generator_add_dots(&$image, $width, $height, $colors) {

  $noise_quantity = $width * $height * ((int) variable_get('image_captcha_noise_level', 5)) / 10.0;

  for ($i = 0; $i < $noise_quantity; $i++) {

    imagesetpixel($image, mt_rand(0, $width), mt_rand(0, $height), $colors[array_rand($colors)]);

  }

}

/**

 * Helper function for drawing text on the image.

 */

function _image_captcha_image_generator_print_string(&$image, $width, $height, $fonts, $font_size, $text, $rtl = FALSE) {

  // Get characters.

  $characters = _image_captcha_utf8_split($text);

  $character_quantity = count($characters);

  // Get colors.

  $background_rgb = _image_captcha_hex_to_rgb(variable_get('image_captcha_background_color', '#ffffff'));

  $foreground_rgb = _image_captcha_hex_to_rgb(variable_get('image_captcha_foreground_color', '#000000'));

  $background_color = imagecolorallocate($image, $background_rgb[0], $background_rgb[1], $background_rgb[2]);

  $foreground_color = imagecolorallocate($image, $foreground_rgb[0], $foreground_rgb[1], $foreground_rgb[2]);

  // Precalculate the value ranges for color randomness.

  $foreground_randomness = (int) (variable_get('image_captcha_foreground_color_randomness', 100));

  if ($foreground_randomness) {

    $foreground_color_range = array();

    for ($i = 0; $i < 3; $i++) {

      $foreground_color_range[$i] = array(

        max(0, $foreground_rgb[$i] - $foreground_randomness),

        min(255, $foreground_rgb[$i] + $foreground_randomness),

      );

    }

  }

  // Set default text color.

  $color = $foreground_color;

  // The image is seperated in different character cages, one for each character,

  // each character will be somewhere inside that cage.

  $ccage_width = $width / $character_quantity;

  $ccage_height = $height;

  foreach ($characters as $c => $character) {

    // Initial position of character: in the center of its cage.

    $center_x = ($c + 0.5) * $ccage_width;

    if ($rtl) {

      $center_x = $width - $center_x;

    }

    $center_y = 0.5 * $height;

    // Pick a random font from the list.

    $font = $fonts[array_rand($fonts)];

    // Get character dimensions for TrueType fonts.

    if ($font != 'BUILTIN') {

      $bbox = imagettfbbox($font_size, 0, drupal_realpath($font), $character);

      // In very rare cases with some versions of the GD library, the x-value

      // of the left side of the bounding box as returned by the first call of

      // imagettfbbox is corrupt (value -2147483648 = 0x80000000).

      // The weird thing is that calling the function a second time

      // can be used as workaround.

      // This issue is discussed at http://drupal.org/node/349218.

      if ($bbox[2] < 0) {

        $bbox = imagettfbbox($font_size, 0, drupal_realpath($font), $character);

      }

    }

    else {

      $character_width = imagefontwidth(5);

      $character_height = imagefontheight(5);

      $bbox = array(

        0,

        $character_height,

        $character_width,

        $character_height,

        $character_width,

        0,

        0,

        0,

      );

    }

    // Random (but small) rotation of the character.

    // TODO: add a setting for this?

    $angle = mt_rand(-10, 10);

    // Determine print position: at what coordinate should the character be

    // printed so that the bounding box would be nicely centered in the cage?

    $bb_center_x = .5 * ($bbox[0] + $bbox[2]);

    $bb_center_y = .5 * ($bbox[1] + $bbox[7]);

    $angle_cos = cos($angle * 3.1415 / 180);

    $angle_sin = sin($angle * 3.1415 / 180);

    $pos_x = $center_x - ($angle_cos * $bb_center_x + $angle_sin * $bb_center_y);

    $pos_y = $center_y - (-$angle_sin * $bb_center_x + $angle_cos * $bb_center_y);

    // Calculate available room to jitter: how much can the character be moved

    // so that it stays inside its cage?

    $bb_width = $bbox[2] - $bbox[0];

    $bb_height = $bbox[1] - $bbox[7];

    $dev_x = .5 * max(0, $ccage_width - abs($angle_cos) * $bb_width - abs($angle_sin) * $bb_height);

    $dev_y = .5 * max(0, $ccage_height - abs($angle_cos) * $bb_height - abs($angle_sin) * $bb_width);

    // Add jitter to position.

    $pos_x = $pos_x + mt_rand(-$dev_x, $dev_x);

    $pos_y = $pos_y + mt_rand(-$dev_y, $dev_y);

    // Calculate text color in case of randomness.

    if ($foreground_randomness) {

      $color = imagecolorallocate($image,

        mt_rand($foreground_color_range[0][0], $foreground_color_range[0][1]),

        mt_rand($foreground_color_range[1][0], $foreground_color_range[1][1]),

        mt_rand($foreground_color_range[2][0], $foreground_color_range[2][1])

      );

    }

    // Draw character.

    if ($font == 'BUILTIN') {

      imagestring($image, 5, $pos_x, $pos_y, $character, $color);

    }

    else {

      imagettftext($image, $font_size, $angle, $pos_x, $pos_y, $color, drupal_realpath($font), $character);

    }

    // For debugging purposes: draw character bounding box (only valid when rotation is disabled).

    // imagerectangle($image, $pos_x + $bbox[0], $pos_y + $bbox[1], $pos_x + $bbox[2], $pos_y + $bbox[7], $color);

  }

  // Return a sign of success.

  return TRUE;

}