changed HSL to HSV conversion method, fixes issue #27

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 All Notable changes to `iris` will be documented in this file.
 
+## 2021-01-31
+- Fix HSL to HSV conversion.
+
 ## 2020-12-06
 - PHP 8.0 support.
 

src/Color/Hsl.php

@@ -54,16 +54,17 @@ public function toHsla()
     }
 
     /**
+     * Source: https://en.wikipedia.org/wiki/HSL_and_HSV#Interconversion
+     *
      * @throws \OzdemirBurak\Iris\Exceptions\InvalidColorException
      * @return \OzdemirBurak\Iris\Color\Hsv
      */
     public function toHsv()
     {
         [$h, $s, $l] = $this->valuesInUnitInterval();
-        $t = $s * $l < 0.5 ? $l : 1 - $l;
-        $s = 2 * $t / ($l + $t);
-        $l += $t;
-        $code = implode(',', [round($h * 360), round($s * 100), round($l * 100)]);
+        $v = $s * min($l, 1 - $l) + $l;
+        $s = $v ? 2 * (1 - $l / $v) : 0;
+        $code = implode(',', [round($h * 360), round($s * 100), round($v * 100)]);
         return new Hsv($code);
     }
 

src/Color/Hsv.php

@@ -42,14 +42,17 @@ public function toHex()
     }
 
     /**
+     * Source: https://en.wikipedia.org/wiki/HSL_and_HSV#Interconversion
+     *
      * @throws \OzdemirBurak\Iris\Exceptions\InvalidColorException
      * @return \OzdemirBurak\Iris\Color\Hsl
      */
     public function toHsl()
     {
         [$h, $s, $v] = $this->valuesInUnitInterval();
-        $l = (2 - $s) * $v / 2;
-        $s = $l && $l < 1 ? $s * $v / ($l < 0.5 ? $l * 2 : 2 - $l * 2) : $s;
+        $l = $v * (1 - $s / 2);
+        $m = min($l, 1 - $l);
+        $s = $l && $l < 1 ? ($v - $l) / $m : 0;
         $code = implode(',', [round($h * 360), round($s * 100), round($l * 100)]);
         return new Hsl($code);
     }

tests/Color/FactoryTest.php

@@ -94,4 +94,14 @@ public function testAmbiguousString()
         $this->expectException(\OzdemirBurak\Iris\Exceptions\AmbiguousColorString::class);
         Factory::init('100, 20%, 5%');
     }
+
+    /**
+     * @throws \OzdemirBurak\Iris\Exceptions\AmbiguousColorString
+     * @throws \OzdemirBurak\Iris\Exceptions\InvalidColorException
+     */
+    public function testSelfConversion()
+    {
+        $this->assertEquals(Factory::init("hsv(0, 36%, 72%)")->toHsl()->toHsv(), new Hsv("hsv(0, 36%, 72%)"));
+        $this->assertEquals(Factory::init("hsl(0, 33%, 66%)")->toHsv()->toHsl(), new Hsl("hsl(0, 33%, 66%)"));
+    }
 }