Perform dependency check on driver creation

src/Drivers/AbstractDriver.php

@@ -11,6 +11,11 @@ use ReflectionClass;
 
 abstract class AbstractDriver implements DriverInterface
 {
+    public function __construct()
+    {
+        $this->checkHealth();
+    }
+
     /**
      * Return a specialized version for the current driver of the given object
      *

src/Drivers/Gd/Driver.php

@@ -3,6 +3,7 @@
 namespace Intervention\Image\Drivers\Gd;
 
 use Intervention\Image\Drivers\AbstractDriver;
+use Intervention\Image\Exceptions\RuntimeException;
 use Intervention\Image\Image;
 use Intervention\Image\Interfaces\ColorInterface;
 use Intervention\Image\Interfaces\ColorProcessorInterface;
@@ -22,6 +23,20 @@ class Driver extends AbstractDriver
         return 'GD';
     }
 
+    /**
+     * {@inheritdoc}
+     *
+     * @see DriverInterface::checkHealth()
+     */
+    public function checkHealth(): void
+    {
+        if (!extension_loaded('gd') || !function_exists('gd_info')) {
+            throw new RuntimeException(
+                'GD Library extension not available with this PHP installation.'
+            );
+        }
+    }
+
     /**
      * {@inheritdoc}
      *

src/Drivers/Imagick/Driver.php

@@ -5,6 +5,7 @@ namespace Intervention\Image\Drivers\Imagick;
 use Imagick;
 use ImagickPixel;
 use Intervention\Image\Drivers\AbstractDriver;
+use Intervention\Image\Exceptions\RuntimeException;
 use Intervention\Image\Image;
 use Intervention\Image\Interfaces\ColorInterface;
 use Intervention\Image\Interfaces\ColorProcessorInterface;
@@ -24,6 +25,20 @@ class Driver extends AbstractDriver
         return 'Imagick';
     }
 
+    /**
+     * {@inheritdoc}
+     *
+     * @see DriverInterface::checkHealth()
+     */
+    public function checkHealth(): void
+    {
+        if (!extension_loaded('imagick') || !class_exists('Imagick')) {
+            throw new RuntimeException(
+                'ImageMagick extension not available with this PHP installation.'
+            );
+        }
+    }
+
     /**
      * {@inheritdoc}
      *

src/Interfaces/DriverInterface.php

@@ -51,4 +51,11 @@ interface DriverInterface
      * @return ColorProcessorInterface
      */
     public function colorProcessor(ColorspaceInterface $colorspace): ColorProcessorInterface;
+
+    /**
+     * Check whether all requirements for operating the driver are met
+     *
+     * @return void
+     */
+    public function checkHealth(): void;
 }