function mandel($params)
{
$image_x = 4 * $params['w'];
$image_y = 4 * $params['h'];
$image = imagecreatetruecolor($image_x, $image_y);
imagefilledrectangle($image, 0, 0, $image_x, $image_y, 0xffffff);
$f = imagecolorallocate($image, $params['r'], $params['g'], $params['b']);
$color = color($params, $image);
for ($x = 0; $x < $image_x; $x++) {
for ($y = 0; $y < $image_y; $y++) {
$c_r = $x / $params['w'] + -2;
$c_i = $y / $params['h'] + -2;
$z_r = 0;
$z_i = 0;
$i = 0;
while ($z_r * $z_r + $z_i * $z_i < 4 and $i < $params['n']) {
$mod = sqrt($z_r * $z_r + $z_i * $z_i);
$arg = atan2($z_i, $z_r);
$z_r = pow($mod, $params['k']) * cos($params['k'] * $arg) + $c_r;
$z_i = pow($mod, $params['k']) * sin($params['k'] * $arg) + $c_i;
$i++;
}
if ($i == $params['n']) {
imagesetpixel($image, $x, $y, $f);
} else {
imagesetpixel($image, $x, $y, $color[$i]);
}
}
}
return send_image($image);
}
function display_img_error($str)
{
global $img_type;
$imageW = 560;
$imageH = 80;
$text_font = 3;
$im = imagecreate($imageW, $imageH);
$black = imagecolorallocate($im, 0, 0, 0);
$gray1 = convertToRGB('EAEAEA');
$gray1 = imagecolorallocate($im, $gray1->red, $gray1->green, $gray1->blue);
//
// Création du contour noir
//
imagefill($im, 0, 0, $black);
imagefilledrectangle($im, 1, 1, $imageW - 2, $imageH - 2, $gray1);
//
// titre du graphe
//
$startW = ($imageW - imagefontwidth($text_font) * strlen($str)) / 2;
$startH = ($imageH - imagefontheight($text_font)) / 2;
imagestring($im, $text_font, $startW, $startH, $str, $black);
send_image('error', $im);
}