PHP HSV 到 RGB 公式理解

Question

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;
 }

但是如何将 HSV 转换为 < PHP 中的strong>RGB？？？

以下是维基百科上的内容，但我不明白，

我猜它很明显

Answer 1

这适用于 [0,1] 范围内的 HSV 值（并给出 [0,1] 范围内的 RGB 值，而不是 {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);
}

Answer 2

将 HSL 的滚动答案从 C 翻译为 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);
}

Answer 3

发现这篇文章太晚了，我的替代方案：

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;
  }

Answer 4

private class HSLPixel{
        double hue;
        double saturation;
        double lightness;

        .... your code
}

public Color HSLToRGB(HSLPixel pixel){

            double v;
            double r,g,b;
            double l = pixel.lightness;
            double h = pixel.hue;
            double s = pixel.saturation;

            r = l;   // default to gray
            g = l;
            b = l;
            v = (l <= 0.5) ? (l * (1.0 + s)) : (l + s - l * s);
            if (v > 0){
                  double m;
                  double sv;
                  int sextant;
                  double fract, vsf, mid1, mid2;

                  m = l + l - v;
                  sv = (v - m ) / v;
                  h *= 6.0;
                  sextant = (int)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;
                  }
            }
            Color rgb = new Color((int)(r * 255.0), (int)(g * 255.0), (int)(b * 255.0));
            return rgb;
    }

Answer 5

ColorJizz 允许您在多种格式之间进行转换。还有一个 PHP 版本。