Implement ColorInterface::isTransparent()

src/Colors/Cmyk/Color.php

@@ -90,4 +90,9 @@ class Color extends AbstractColor
             $this->yellow()->value(),
         ]);
     }
+
+    public function isTransparent(): bool
+    {
+        return false;
+    }
 }

src/Colors/Hsl/Color.php

@@ -107,4 +107,14 @@ class Color extends AbstractColor
     {
         return $this->saturation()->value() == 0;
     }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @see ColorInterface::isTransparent()
+     */
+    public function isTransparent(): bool
+    {
+        return false;
+    }
 }

src/Colors/Hsv/Color.php

@@ -107,4 +107,14 @@ class Color extends AbstractColor
     {
         return $this->saturation()->value() == 0;
     }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @see ColorInterface::isTransparent()
+     */
+    public function isTransparent(): bool
+    {
+        return false;
+    }
 }

src/Colors/Rgb/Color.php

@@ -109,31 +109,26 @@ class Color extends AbstractColor
      */
     public function toHex(string $prefix = ''): string
     {
-        if ($this->isFullyOpaque()) {
+        if ($this->isTransparent()) {
             return sprintf(
-                '%s%02x%02x%02x',
+                '%s%02x%02x%02x%02x',
                 $prefix,
                 $this->red()->value(),
                 $this->green()->value(),
-                $this->blue()->value()
+                $this->blue()->value(),
+                $this->alpha()->value()
             );
         }
 
         return sprintf(
-            '%s%02x%02x%02x%02x',
+            '%s%02x%02x%02x',
             $prefix,
             $this->red()->value(),
             $this->green()->value(),
-            $this->blue()->value(),
+            $this->blue()->value()
-            $this->alpha()->value()
         );
     }
 
-    public function isFullyOpaque(): bool
-    {
-        return $this->alpha()->value() === 255;
-    }
-
     /**
      * {@inheritdoc}
      *
@@ -141,21 +136,21 @@ class Color extends AbstractColor
      */
     public function toString(): string
     {
-        if ($this->isFullyOpaque()) {
+        if ($this->isTransparent()) {
             return sprintf(
-                'rgb(%d, %d, %d)',
+                'rgba(%d, %d, %d, %.1F)',
                 $this->red()->value(),
                 $this->green()->value(),
-                $this->blue()->value()
+                $this->blue()->value(),
+                $this->alpha()->normalize(),
             );
         }
 
         return sprintf(
-            'rgba(%d, %d, %d, %.1F)',
+            'rgb(%d, %d, %d)',
             $this->red()->value(),
             $this->green()->value(),
-            $this->blue()->value(),
+            $this->blue()->value()
-            $this->alpha()->normalize(),
         );
     }
 
@@ -170,4 +165,14 @@ class Color extends AbstractColor
 
         return count(array_unique($values, SORT_REGULAR)) === 1;
     }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @see ColorInterface::isTransparent()
+     */
+    public function isTransparent(): bool
+    {
+        return $this->alpha()->value() < $this->alpha()->max();
+    }
 }

src/Interfaces/ColorInterface.php

@@ -83,4 +83,11 @@ interface ColorInterface
      * @return bool
      */
     public function isGreyscale(): bool;
+
+    /**
+     * Determine if the current color is (semi) transparent
+     *
+     * @return bool
+     */
+    public function isTransparent(): bool;
 }

tests/Unit/Colors/Cmyk/ColorTest.php

@@ -105,4 +105,10 @@ final class ColorTest extends BaseTestCase
         $color = new Color(100, 50, 20, 0);
         $this->assertEquals('cmyk(100%, 50%, 20%, 0%)', (string) $color);
     }
+
+    public function testIsTransparent(): void
+    {
+        $color = new Color(100, 50, 50, 0);
+        $this->assertFalse($color->isTransparent());
+    }
 }

tests/Unit/Colors/Hsl/ColorTest.php

@@ -102,4 +102,10 @@ final class ColorTest extends BaseTestCase
         $color = new Color(0, 0, 1);
         $this->assertTrue($color->isGreyscale());
     }
+
+    public function testIsTransparent(): void
+    {
+        $color = new Color(0, 1, 0);
+        $this->assertFalse($color->isTransparent());
+    }
 }

tests/Unit/Colors/Hsv/ColorTest.php

@@ -102,4 +102,10 @@ final class ColorTest extends BaseTestCase
         $color = new Color(0, 0, 1);
         $this->assertTrue($color->isGreyscale());
     }
+
+    public function testIsTransparent(): void
+    {
+        $color = new Color(1, 0, 0);
+        $this->assertFalse($color->isTransparent());
+    }
 }

tests/Unit/Colors/Rgb/ColorTest.php

@@ -148,4 +148,19 @@ final class ColorTest extends BaseTestCase
         $color = new Color(50, 50, 50);
         $this->assertTrue($color->isGreyscale());
     }
+
+    public function testIsTransparent(): void
+    {
+        $color = new Color(255, 255, 255);
+        $this->assertFalse($color->isTransparent());
+
+        $color = new Color(255, 255, 255, 255);
+        $this->assertFalse($color->isTransparent());
+
+        $color = new Color(255, 255, 255, 85);
+        $this->assertTrue($color->isTransparent());
+
+        $color = new Color(255, 255, 255, 0);
+        $this->assertTrue($color->isTransparent());
+    }
 }