function hex2rgb($hex) {

$color = str_replace(‘#‘,‘‘,$hex);

$rgb = array(‘r‘ => hexdec(substr($color,0,2)),

‘g‘ => hexdec(substr($color,2,2)),

‘b‘ => hexdec(substr($color,4,2)));

return $rgb;

} // www.jb51.net

function rgb2cmyk($var1,$g=0,$b=0) {

if (is_array($var1)) {

$r = $var1[‘r‘];

$g = $var1[‘g‘];

$b = $var1[‘b‘];

} else {

$r=$var1;

}

$cyan = 255 - $r;

$magenta = 255 - $g;

$yellow = 255 - $b;

$black = min($cyan, $magenta, $yellow);

$cyan = @(($cyan - $black) / (255 - $black)) * 255;

$magenta = @(($magenta - $black) / (255 - $black)) * 255;

$yellow = @(($yellow - $black) / (255 - $black)) * 255;

return array(‘c‘ => $cyan / 255,

‘m‘ => $magenta / 255,

‘y‘ => $yellow / 255,

‘k‘ => $black / 255);

}

$color=rgb2cmyk(hex2rgb(‘#FF0000‘));

原文：http://www.jb51.net/article/52872.htm