PHP HSV 到 RGB 公式理解

php colors rgb hsv

2022-08-31 00:52:31

我可以使用以下代码将RGB值转换为HSV...

 $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;
 }

但是如何在PHP中将HSV转换为RGB???

以下内容在维基百科上，但我不明白，

我猜这很明显

alt text

答案 1

这适用于该范围内的 HSV 值（并在该范围内给出 RGB 值，而不是：[0,1][0,1]{0, 1, ..., 255}

function HSVtoRGB(array $hsv) {
    list($H,$S,$V) = $hsv;
    //1
    $H *= 6;
    //2
    $I = floor($H);
    $F = $H - $I;
    //3
    $M = $V * (1 - $S);
    $N = $V * (1 - $S * $F);
    $K = $V * (1 - $S * (1 - $F));
    //4
    switch ($I) {
        case 0:
            list($R,$G,$B) = array($V,$K,$M);
            break;
        case 1:
            list($R,$G,$B) = array($N,$V,$M);
            break;
        case 2:
            list($R,$G,$B) = array($M,$V,$K);
            break;
        case 3:
            list($R,$G,$B) = array($M,$N,$V);
            break;
        case 4:
            list($R,$G,$B) = array($K,$M,$V);
            break;
        case 5:
        case 6: //for when $H=1 is given
            list($R,$G,$B) = array($V,$M,$N);
            break;
    }
    return array($R, $G, $B);
}

答案 2

将 HSL 的卷轴答案从 C 转换为 PHP

function ColorHSLToRGB($h, $s, $l){

        $r = $l;
        $g = $l;
        $b = $l;
        $v = ($l <= 0.5) ? ($l * (1.0 + $s)) : ($l + $s - $l * $s);
        if ($v > 0){
              $m;
              $sv;
              $sextant;
              $fract;
              $vsf;
              $mid1;
              $mid2;

              $m = $l + $l - $v;
              $sv = ($v - $m ) / $v;
              $h *= 6.0;
              $sextant = floor($h);
              $fract = $h - $sextant;
              $vsf = $v * $sv * $fract;
              $mid1 = $m + $vsf;
              $mid2 = $v - $vsf;

              switch ($sextant)
              {
                    case 0:
                          $r = $v;
                          $g = $mid1;
                          $b = $m;
                          break;
                    case 1:
                          $r = $mid2;
                          $g = $v;
                          $b = $m;
                          break;
                    case 2:
                          $r = $m;
                          $g = $v;
                          $b = $mid1;
                          break;
                    case 3:
                          $r = $m;
                          $g = $mid2;
                          $b = $v;
                          break;
                    case 4:
                          $r = $mid1;
                          $g = $m;
                          $b = $v;
                          break;
                    case 5:
                          $r = $v;
                          $g = $m;
                          $b = $mid2;
                          break;
              }
        }
        return array('r' => $r * 255.0, 'g' => $g * 255.0, 'b' => $b * 255.0);
}