function _image_captcha_image_generator_print_string in CAPTCHA 6.2

Same name and namespace in other branches

1. 5.3 image_captcha/image_captcha.user.inc \_image_captcha_image_generator_print_string()
2. 6 image_captcha/image_captcha.user.inc \_image_captcha_image_generator_print_string()
3. 7 image_captcha/image_captcha.user.inc \_image_captcha_image_generator_print_string()

Helper function for drawing text on the image.

1 call to _image_captcha_image_generator_print_string()

_image_captcha_generate_image in image_captcha/image_captcha.user.inc

Base function for generating a image CAPTCHA.

File

image_captcha/image_captcha.user.inc, line 238

Functions for the generation of the CAPTCHA image.

Code

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, 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, 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?
    $bb_center_x = 0.5 * ($bbox[0] + $bbox[2]);
    $bb_center_y = 0.5 * ($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 = 0.5 * max(0, $ccage_width - abs($angle_cos) * $bb_width - abs($angle_sin) * $bb_height);
    $dev_y = 0.5 * 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, $color, realpath($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;
}