Build an Image and initialize to background color; write to output file

src/fart/Engine.cpp

@@ -66,5 +66,19 @@ int Engine::run(string_view input_file, opt<string_view> output_file)
     options.merge(scene->options);
     options.apply_defaults();
 
+    Image image(*options.width, *options.height);
+    for (size_t y = 0u; y < *options.height; y++)
+    {
+        for (size_t x = 0u; x < *options.width; x++)
+        {
+            image[x, y] = *options.background;
+        }
+    }
+
+    if (!image_writer->write(image))
+    {
+        return 1;
+    }
+
     return 0;
 }