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run code in 300+ PHP versions simultaneously
<?php function rgb2cmyk($r, $g, $b) { $c = 255 - $r; $m = 255 - $g; $y = 255 - $b; $b = min($c, $m, $y); $c = round(($c - $b) / (255 - $b)); $m = round(($m - $b) / (255 - $b)); $y = round(($y - $b) / (255 - $b)); $k = round($b / 255); return array($c, $m, $y, $k); } function cmyk2rgb($c, $m, $y, $k) { $r = 255 - round(255 * ($c - $c * $k - $k)); $g = 255 - round(255 * ($m - $m * $k - $k)); $b = 255 - round(255 * ($y - $y * $k - $k)); return array($r, $g, $b); } for ($i = 0; $i < 20; $i++) { $r = rand() % 255; $g = rand() % 255; $b = rand() % 255; echo "$i. $r, $g, $b -> "; $cmyk = rgb2cmyk($r, $g, $b); echo "{$cmyk[0]}, {$cmyk[1]}, {$cmyk[2]}, {$cmyk[3]} -> "; $rgb = cmyk2rgb($cmyk[0], $cmyk[1], $cmyk[2], $cmyk[3]); echo "{$rgb[0]}, {$rgb[1]}, {$rgb[2]}"; echo "\n"; }

preferences:
33.51 ms | 402 KiB | 5 Q