<?php

set_time_limit(999);

$maxIterations = 100;

$imgWidth = isset($_GET['width']) ? max(1, min(4096, (int)preg_replace('/\D/', '', $_GET['width']))) : 700;
$imgHeight = isset($_GET['height']) ? max(1, min(2160, (int)preg_replace('/\D/', '', $_GET['height']))) : 433;

$gd = imagecreatetruecolor($imgWidth, $imgHeight);
$black = imagecolorallocate($gd, 0, 0, 0);

$K_real = 0.233 + (rand(1, 8000) / 71421);
$K_img = 0.505 + (rand(1, 9999) / 142842);

$zoomFactor = (1 - (rand(1, 9999) / 20000));

$minReal = -1.0 * $zoomFactor;
$maxReal = 1.0 * $zoomFactor;
$minImg = (-0.9 - (rand(0, 2) / 10)) * $zoomFactor;
$maxImg = $minImg + ($maxReal - $minReal) * ($imgHeight / $imgWidth);

$Re_factor = ($maxReal - $minReal) / ($imgWidth - 1);
$Im_factor = ($maxImg - $minImg) / ($imgHeight - 1);

$colors = [
    [66, 30, 15],
    [25, 7, 26],
    [9, 1, 47],
    [4, 4, 73],
    [0, 7, 100],
    [12, 44, 138],
    [24, 82, 177],
    [57, 125, 209],
    [134, 181, 229],
    [211, 236, 248],
    [241, 233, 191],
    [248, 201, 95],
    [255, 170, 0],
    [204, 128, 0],
    [153, 87, 0],
    [106, 52, 3]
];

$bands = rand(1, 4);
$brightnessFactor = rand(90, 100) / 100;

function smoothColor($iteration, $maxIterations, $Z_real, $Z_img, $colors, $bands, $brightnessFactor) {
    if ($iteration == $maxIterations) {
        return [0, 0, 0];
    }
    $mu = $iteration + 1 - log(log($Z_real * $Z_real + $Z_img * $Z_img)) / log(2);
    $mu = $mu / $maxIterations; // Normalize to [0, 1]
    $mu *= $bands * (count($colors) - 1);
    $colorIndex1 = floor($mu) % count($colors);
    $colorIndex2 = ($colorIndex1 + 1) % count($colors);
    $f = $mu - floor($mu);
    $r = (1 - $f) * $colors[$colorIndex1][0] + $f * $colors[$colorIndex2][0];
    $g = (1 - $f) * $colors[$colorIndex1][1] + $f * $colors[$colorIndex2][1];
    $b = (1 - $f) * $colors[$colorIndex1][2] + $f * $colors[$colorIndex2][2];
    $r = $r * $brightnessFactor;
    $g = $g * $brightnessFactor;
    $b = $b * $brightnessFactor;
    $r = max(0, min(255, (int)$r));
    $g = max(0, min(255, (int)$g));
    $b = max(0, min(255, (int)$b));
    return [$r, $g, $b];
}

$samples = 2;  // 2x2 antialiasing

for ($y = 0; $y < $imgHeight; ++$y) {
    for ($x = 0; $x < $imgWidth; ++$x) {
        $colorSum = [0, 0, 0];
        for ($j = 0; $j < $samples; ++$j) {
            for ($i = 0; $i < $samples; ++$i) {
                $c_real = $minReal + ($x + $i / $samples) * $Re_factor;
                $c_img = $maxImg - ($y + $j / $samples) * $Im_factor;
                $Z_real = $c_real;
                $Z_img = $c_img;
                $iteration = 0;
                while ($iteration < $maxIterations) {
                    $Z_real2 = $Z_real * $Z_real;
                    $Z_img2 = $Z_img * $Z_img;
                    if (($Z_real2 + $Z_img2) > 4) {
                        break;
                    }
                    $Z_img = 2 * $Z_real * $Z_img + $K_img;
                    $Z_real = $Z_real2 - $Z_img2 + $K_real;
                    $iteration++;
                }
                $rgb = ($iteration == $maxIterations) ? [0, 0, 0] : smoothColor($iteration, $maxIterations, $Z_real, $Z_img, $colors, $bands, $brightnessFactor);
                $colorSum[0] += $rgb[0];
                $colorSum[1] += $rgb[1];
                $colorSum[2] += $rgb[2];
            }
        }
        $finalColor = [
            (int)($colorSum[0] / ($samples * $samples)),
            (int)($colorSum[1] / ($samples * $samples)),
            (int)($colorSum[2] / ($samples * $samples))
        ];
        $color = imagecolorallocate($gd, $finalColor[0], $finalColor[1], $finalColor[2]);
        imagesetpixel($gd, $x, $y, $color);
    }
}

header('Content-Type: image/png');
imagepng($gd);
imagedestroy($gd);

?>