Die Transformung von CMYK zu RGB erfolgt über HSV.

src/Transformer/CyanMagentaYellowKeyTransformer.php

@@ -24,19 +24,8 @@ class CyanMagentaYellowKeyTransformer implements ColorModelTransformInterface
 
     public function toRedGreenBlue(): RedGreenBlue
     {
-        $cyan = $this->color->getCyan();
-        $magenta = $this->color->getMagenta();
-        $yellow = $this->color->getYellow();
-        $key = $this->color->getKey();
-
-        $red = 0;
-        $green = 0;
-        $blue = 0;
-
-        return (new RedGreenBlue())
-            ->setRed($red)
-            ->setGreen($green)
-            ->setBlue($blue);
+        $hsv_color = (new Utilities\CyanMagentaYellowKeyToHueSaturationValue($this->color))->convert();
+        return (new Utilities\HueSaturationValueToRedGreenBlue($hsv_color))->convert();
     }
 
     public function toCyanMagentaYellowKey(): CyanMagentaYellowKey

src/Transformer/Utilities/HueSaturationValueToRedGreenBlue.php

@@ -0,0 +1,56 @@
+<?php
+
+
+namespace TorstenHettstedt\Colors\Transformer\Utilities;
+
+
+use TorstenHettstedt\Colors\ColorModels\HueSaturationValue;
+use TorstenHettstedt\Colors\ColorModels\RedGreenBlue;
+
+class HueSaturationValueToRedGreenBlue
+{
+    // Daten für HSV
+    /** @var float : Definition des Farbton als Anteil eines Vollkreises '$Hue * π' */
+    protected float $hue;
+    /** @var float : Definition der Sättigung der Farbe */
+    protected float $saturation;
+    /** @var float : Definition der Helligkeit der Farbe */
+    protected float $value;
+
+    // Daten für RGB
+    /** @var float : Definition des Rotanteil */
+    protected float $red = 1.0;
+    /** @var float : Definition des Grünanteil */
+    protected float $green = 1.0;
+    /** @var float : Definition des Blauanteil */
+    protected float $blu = 1.0;
+
+    /**
+     * HueSaturationValueToRedGreenBlue constructor.
+     * @param HueSaturationValue $from_color
+     * @noinspection PhpPureAttributeCanBeAddedInspection
+     */
+    public function __construct(HueSaturationValue $from_color)
+    {
+        $this->hue = $from_color->getHue();
+        $this->saturation = $from_color->getSaturation();
+        $this->value = $from_color->getValue();
+    }
+
+    public function convert(): RedGreenBlue
+    {
+        $this->processConvert();
+
+        return (new RedGreenBlue())
+            ->setRed($this->red)
+            ->setGreen($this->green)
+            ->setBlue($this->blu);
+    }
+
+
+    protected function processConvert(): void
+    {
+
+    }
+
+}

tests/unit/Transformer/CyanMagentaYellowKeyTransformerTest.php

@@ -222,8 +222,6 @@ class CyanMagentaYellowKeyTransformerTest extends Unit
      */
     public function testToRedGreenBlue(array $cmyk, array $rgb)
     {
-        $this->markTestSkipped('Das Verhalten muss über HSL erforscht werden.');
-
         $this->color = $this->make(CyanMagentaYellowKey::class, $cmyk);
 
         $transformer = new CyanMagentaYellowKeyTransformer($this->color);