Color Conversion Functions

[MikeSnead]

Not exactly the most well formed code (I wrote it back when I had fun compressing scripts as much as I could) but it has so far worked well. Thought it might be useful for someone someday for some strange reason 🙂

Convert back and forth between RGB and Hue/Sat/Brightness color values.

<?php

function RGB_to_HSV ( $r , $g , $b )
{
	$r = $r/255;
	$g = $g/255;
	$b = $b/255;

$MAX = max($r,$g,$b);
$MIN = min($r,$g,$b);

if     ($MAX == $MIN) return array(0,0,$MAX);
if     ($r == $MAX) $HUE = ((0 + (($g - $b)/($MAX-$MIN))) * 60);
elseif ($g == $MAX) $HUE = ((2 + (($b - $r)/($MAX-$MIN))) * 60);
elseif ($b == $MAX) $HUE = ((4 + (($r - $g)/($MAX-$MIN))) * 60);
if     ( $HUE < 0 ) $HUE += 360;

return array($HUE,(($MAX - $MIN)/$MAX),$MAX);
}

function HSV_to_RGB ( $H , $S , $V )
{	
	if ($S == 0) return array($V * 255,$V * 255,$V * 255);

$Hi = floor($H/60);
$f  = (($H/60) - $Hi);
$p  = ($V * (1 - $S));
$q  = ($V * (1 - ($S * $f)));
$t  = ($V * (1 - ($S * (1 - $f))));

switch ( $Hi )
{
	case 0  : $red = $V; $gre = $t; $blu = $p; break;
	case 1  : $red = $q; $gre = $V; $blu = $p; break;
	case 2  : $red = $p; $gre = $V; $blu = $t; break;
	case 3  : $red = $p; $gre = $q; $blu = $V; break;
	case 4  : $red = $t; $gre = $p; $blu = $V; break;
	case 5  : $red = $V; $gre = $p; $blu = $q; break;
	default : exit("error -- invalid parameters\n\n");
}

return array(round($red * 255),round($gre * 255),round($blu * 255));
}

?>

[BuzzLY]

I use very similar code in my color picker. Click on the link in my signature.

[leatherback]

Hey Buzz,

That is a great tool!

Cool. Is the code free/available? Or..?

j.

[BuzzLY]

Thanks.

Yes, you can use it if you like. There is a zip file available -- just click one of the links at the bottom of the Color Picker page.

I don't warrant the code -- use it as is, and modify how you like. All I ask is that you give me credit for the original code, and let me know when you modify it so I can check it out!