Added monochrome Command

monochrome: transform image to black and white (http://imagemagick.org/script/command-line-options.php#monochrome)

Author: JeffAlyanak

Command.php

@@ -475,6 +475,17 @@ public function strip(): self
         return $this;
     }
 
+
+    /**
+     * @see http://imagemagick.org/script/command-line-options.php#monochrome
+     */
+    public function monochrome(): self
+    {
+        $this->command[] = '-monochrome';
+
+        return $this;
+    }
+
     /**
      * @see http://imagemagick.org/script/command-line-options.php#interlace
      */

Tests/CommandTest.php

@@ -140,6 +140,25 @@ public function testColorspaceImage(): void
         $this->testConvertIdentifyImage($imageOutput, 'JPEG', '180x170+0+0', '8-bit');
     }
 
+    public function testMonochrome(): void
+    {
+        $command = new Command(IMAGEMAGICK_DIR);
+
+        $imageSource = $this->resourcesDir.'/moon_180.jpg';
+        $imageOutput = $this->resourcesDir.'/outputs/moon_monochrome.jpg';
+        static::assertFileExists($imageSource);
+
+        $response = $command
+            ->convert($imageSource)
+            ->monochrome()
+            ->file($imageOutput, false)
+            ->run()
+        ;
+
+        static::assertFalse($response->hasFailed());
+        static::assertFileExists($this->resourcesDir.'/outputs/moon_monochrome.jpg');
+    }
+
     /**
      * @dataProvider provideImagesToIdentify
      */