PHP HSV to RGB formula comprehension

user_1246275 0
Viewed 15299

I can convert RGB values to HSV with the following code...

 $r = $r/255;
 $g = $g/255;
 $b = $b/255;

 $h = 0;
 $s = 0;
 $v = 0;

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

 $r = $max-$min;
 $v = $max;


 if($r == 0){
  $h = 0;
  $s = 0;
 }
 else {
  $s = $r / $max;

  $hr = ((($max - $r) / 6) + ($r / 2)) / $r;
  $hg = ((($max - $g) / 6) + ($r / 2)) / $r;
  $hb = ((($max - $b) / 6) + ($r / 2)) / $r;

  if ($r == $max) $h = $hb - $hg;
  else if($g == $max) $h = (1/3) + $hr - $hb;
  else if ($b == $max) $h = (2/3) + $hg - $hr;

  if ($h < 0)$h += 1;
  if ($h > 1)$h -= 1;
 }

But how do you convert HSV to RGB in PHP???

The following is on wikipedia but I don't understand it,

I'm guessing it's pretty obvious

alt text

hsv rgb colors php
6 Answers

Found this post too late, my alternate take on it:

hsv2rgb function PHP

hue: 0-360, sat: 0-100, val: 0-100

  function hsv2rgb($hue,$sat,$val) {;
    $rgb = array(0,0,0);
    //calc rgb for 100% SV, go +1 for BR-range
    for($i=0;$i<4;$i++) {
      if (abs($hue - $i*120)<120) {
        $distance = max(60,abs($hue - $i*120));
        $rgb[$i % 3] = 1 - (($distance-60) / 60);
      }
    }
    //desaturate by increasing lower levels
    $max = max($rgb);
    $factor = 255 * ($val/100);
    for($i=0;$i<3;$i++) {
      //use distance between 0 and max (1) and multiply with value
      $rgb[$i] = round(($rgb[$i] + ($max - $rgb[$i]) * (1 - $sat/100)) * $factor);
    }
    $rgb['html'] = sprintf('#%02X%02X%02X', $rgb[0], $rgb[1], $rgb[2]);
    return $rgb;
  }
user_2472450
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