Magnifier: Add brightness and contrast functionality

Added clutter effects class that does lightness inversion.
Modified the magnifier to use this inversion effect.

https://bugzilla.gnome.org/show_bug.cgi?id=639851

src/shell-invert-lightness-effect.h

@@ -0,0 +1,42 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+/*
+ * Copyright © 2010-2012 Inclusive Design Research Centre, OCAD University.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author:
+ *   Joseph Scheuhammer <clown@alum.mit.edu>
+ */
+#ifndef __SHELL_INVERT_LIGHTNESS_EFFECT_H__
+#define __SHELL_INVERT_LIGHTNESS_EFFECT_H__
+
+#define COGL_ENABLE_EXPERIMENTAL_API
+#include <clutter/clutter.h>
+
+G_BEGIN_DECLS
+
+#define SHELL_TYPE_INVERT_LIGHTNESS_EFFECT        (shell_invert_lightness_effect_get_type ())
+#define SHELL_INVERT_LIGHTNESS_EFFECT(obj)        (G_TYPE_CHECK_INSTANCE_CAST ((obj), SHELL_TYPE_INVERT_LIGHTNESS_EFFECT, ShellInvertLightnessEffect))
+#define SHELL_IS_INVERT_LIGHTNESS_EFFECT(obj)     (G_TYPE_CHECK_INSTANCE_TYPE ((obj), SHELL_TYPE_INVERT_LIGHTNESS_EFFECT))
+
+typedef struct _ShellInvertLightnessEffect        ShellInvertLightnessEffect;
+typedef struct _ShellInvertLightnessEffectClass   ShellInvertLightnessEffectClass;
+
+GType shell_invert_lightness_effect_get_type (void) G_GNUC_CONST;
+
+ClutterEffect *shell_invert_lightness_effect_new (void);
+
+G_END_DECLS
+
+#endif /* __SHELL_INVERT_LIGHTNESS_EFFECT_H__ */