### color conversion module ###

package Color::Convert;

sub min { @_ = sort @_; shift; }
sub max { @_ = sort @_; pop; }

sub rgb2hsv {

    # r,g,b values are from 0 to 255
    # h = [0..360], s = [0..100], v = [0..100]
    #		if s == 0, then h = -1 (undefined)
    
    my ($r,$g,$b) = @_;
    
    $r /= 255;
    $g /= 255;
    $b /= 255;

    my ($h, $s, $v);
    my ($min, $max, $delta);
    
    $min = min ( $r, $g, $b );
    $max = max ( $r, $g, $b );

    # value is just the brightest rgb value
    $v = $max;

    # account for shades of gray:
    $delta = $max - $min;
    if ($delta == 0 ) {
	$s = 0; # no hue, so it can't be saturated!
	$h = -1; # hue is really undefined, but...
	return ($h, $s, $v*100);
    }

    # saturation is intensity/blandness of color:
    $s = $delta / $max; # max > 0 or delta would be 0


    # hue depends on the relative strengths of the colors:
    if( $r == $max ) {
	$h = ( $g - $b ) / $delta;	# between yellow & magenta
    } elsif( $g == $max ) {
	$h = 2 + (( $b - $r ) / $delta);	# between cyan & yellow
    } else {
	$h = 4 + (( $r - $g ) / $delta);	# between magenta & cyan
    }

    # it's also calculated as degrees on a color wheel
    $h *= 60;  # degrees
    $h += 360 if ($h < 0); 

    # s and v are percentages
    $s *= 100;
    $v *= 100;
    
    return (int( $h ), int($s), int($v)); # should be rounded, but oh well
}
1;