image_captcha.user.inc in CAPTCHA 5.3
Same filename and directory in other branches
Implementation of the image generation for the image CAPTCHA module.
File
image_captcha/image_captcha.user.incView source
<?php
/**
* @file
* Implementation of the image generation for the image CAPTCHA module.
*/
/**
* base function for generating a image CAPTCHA
*/
function _image_captcha_generate_image($code) {
// get font
list($font, $errmsg) = _image_captcha_get_font();
if (!$font) {
watchdog('CAPTCHA', $errmsg, WATCHDOG_ERROR);
exit;
}
// get other settings
$font_size = (int) variable_get('image_captcha_font_size', 30);
$character_spacing = (double) variable_get('image_captcha_character_spacing', '1.2');
$characters = _image_captcha_utf8_split($code);
$character_quantity = count($characters);
$width = $character_spacing * $font_size * $character_quantity;
$height = 2 * $font_size;
// create image resource
$image = imagecreatetruecolor($width, $height);
if (!$image) {
return FALSE;
}
// get background color and paint
$background_rgb = _image_captcha_hex_to_rgb(variable_get('image_captcha_background_color', '#ffffff'));
$background_color = imagecolorallocate($image, $background_rgb[0], $background_rgb[1], $background_rgb[2]);
imagefilledrectangle($image, 0, 0, $width, $height, $background_color);
// draw text
if (variable_get('image_captcha_double_vision', 0)) {
$result = _image_captcha_image_generator_print_string($image, $width, $height, $font, $font_size, $code, TRUE);
if (!$result) {
return FALSE;
}
}
$result = _image_captcha_image_generator_print_string($image, $width, $height, $font, $font_size, $code, FALSE);
if (!$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 * $font_size * variable_get('image_captcha_distortion_amplitude', 6) / 10.0;
if ($distortion_amplitude > 1) {
// distortion parameters
$wavelength_xr = (2 + 3 * lcg_value()) * $font_size;
$wavelength_yr = (2 + 3 * lcg_value()) * $font_size;
$freq_xr = 2 * 3.141592 / $wavelength_xr;
$freq_yr = 2 * 3.141592 / $wavelength_yr;
$wavelength_xt = (2 + 3 * lcg_value()) * $font_size;
$wavelength_yt = (2 + 3 * lcg_value()) * $font_size;
$freq_xt = 2 * 3.141592 / $wavelength_xt;
$freq_yt = 2 * 3.141592 / $wavelength_yt;
$distorted_image = imagecreatetruecolor($width, $height);
if (!$distorted_image) {
return FALSE;
}
if (variable_get('image_captcha_bilinair_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 $image;
}
}
function _image_captcha_image_generator_add_lines(&$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)]);
}
}
function _image_captcha_image_generator_add_dots(&$image, $width, $height, $colors) {
$noise_quantity = $width * $height / 2.0 * (int) variable_get('image_captcha_noise_level', 5) / 10.0;
for ($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
*
* @param $background_mode if the text is for the background of the double vision mode
*/
function _image_captcha_image_generator_print_string(&$image, $width, $height, $font, $font_size, $text, $background_mode = FALSE) {
// get characters
$characters = _image_captcha_utf8_split($text);
$character_quantity = count($characters);
// get character width for builtin font
if ($font == 'BUILTIN') {
$character_width = imagefontwidth(5);
$character_height = imagefontheight(5);
$bbox = array(
0,
$character_height,
$character_width,
$character_height,
$character_width,
0,
0,
0,
);
}
// get colors
$background_rgb = _image_captcha_hex_to_rgb(variable_get('image_captcha_background_color', '#ffffff'));
$foreground_rgb = _image_captcha_hex_to_rgb(variable_get('image_captcha_foreground_color', '#000000'));
// correct foreground for background mode (double vision)
if ($background_mode) {
for ($i = 0; $i < 3; $i++) {
$foreground_rgb[$i] = 0.75 * $background_rgb[$i] + 0.25 * $foreground_rgb[$i];
}
}
$background_color = imagecolorallocate($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) {
if ($background_mode) {
$foreground_randomness *= 0.25;
}
$foreground_color_range = array();
for ($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;
$center_y = 0.5 * $height;
// get character dimensions for ttf fonts
if ($font != 'BUILTIN') {
$bbox = imagettfbbox($font_size, 0, realpath($font), $character);
}
// determine print position: at what coordinate should the character be
// printed so that the bounding box would be nicely centered in the cage?
$pos_x = $center_x - 0.5 * ($bbox[0] + $bbox[2]);
$pos_y = $center_y - 0.5 * ($bbox[1] + $bbox[7]);
// calculate available room to jitter: how much can the character be moved
// so that it stays inside its cage?
$dev_x = 0.5 * max(0, $ccage_width - ($bbox[2] - $bbox[0]));
$dev_y = 0.5 * max(0, $ccage_height - ($bbox[1] - $bbox[7]));
// 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, 0, $pos_x, $pos_y, $color, realpath($font), $character);
}
// for debugging purposes: draw character bounding box
// imagerectangle($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_generate_image | base function for generating a image CAPTCHA |
| _image_captcha_image_generator_add_dots | |
| _image_captcha_image_generator_add_lines | |
| _image_captcha_image_generator_print_string | Helper function for drawing text on the image |