image_captcha.user.inc in CAPTCHA 7
Same filename and directory in other branches
Functions for the generation of the CAPTCHA image.
Loosely Based on MyCaptcha by Heine Deelstra (http://heine.familiedeelstra.com/mycaptcha-download)
File
image_captcha/image_captcha.user.incView source
<?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 = 0.25 * $font_size * variable_get('image_captcha_distortion_amplitude', 0) / 10.0;
if ($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?
$bb_center_x = 0.5 * ($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, $color, drupal_realpath($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;
}Functions
Name |
Description |
|---|---|
| image_captcha_image | Menu callback function that generates the CAPTCHA image. |
| _image_captcha_generate_image | Base function for generating a image CAPTCHA. |
| _image_captcha_hex_to_rgb | Small helper function for parsing a hexadecimal color to a RGB tuple. |
| _image_captcha_image_generator_add_dots | Add dots. |
| _image_captcha_image_generator_add_lines | Add lines. |
| _image_captcha_image_generator_print_string | Helper function for drawing text on the image. |