Refactor V4L2 and X11 grabbers to share more code

Former-commit-id: 46176e53d1acf39f9bd0c0ecbb8e5fb5ab4d45be

include/grabber/X11Grabber.h

@@ -0,0 +1,37 @@
+
+// Hyperion-utils includes
+#include <utils/Image.h>
+#include <utils/ColorRgb.h>
+
+// X11 includes
+#include <X11/Xlib.h>
+
+class X11Grabber
+{
+public:
+
+	X11Grabber(const unsigned cropHorizontal, const unsigned cropVertical, const unsigned pixelDecimation);
+
+	virtual ~X11Grabber();
+
+	int open();
+
+	Image<ColorRgb> & grab();
+
+private:
+
+	const unsigned _pixelDecimation;
+
+	const unsigned _cropWidth;
+	const unsigned _cropHeight;
+
+	/// Reference to the X11 display (nullptr if not opened)
+	Display * _x11Display;
+
+	unsigned _screenWidth;
+	unsigned _screenHeight;
+
+	Image<ColorRgb> _image;
+
+	int updateScreenDimensions();
+};