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+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+/*
+ * Copyright (C) 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>
+ */
+
+/**
+ * SECTION:shell-invert-lightness-effect
+ * @short_description: A colorization effect where lightness is inverted but
+ * color is not.
+ * @see_also: #ClutterEffect, #ClutterOffscreenEffect
+ *
+ * #ShellInvertLightnessEffect is a sub-class of #ClutterEffect that enhances
+ * the appearance of a clutter actor. Specifically it inverts the lightness
+ * of a #ClutterActor (e.g., darker colors become lighter, white becomes black,
+ * and white, black).
+ */
+
+#define SHELL_INVERT_LIGHTNESS_EFFECT_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST ((klass), SHELL_TYPE_INVERT_LIGHTNESS_EFFECT, ShellInvertLightnessEffectClass))
+#define SHELL_IS_INVERT_EFFECT_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass), SHELL_TYPE_INVERT_LIGHTNESS_EFFECT))
+#define SHELL_INVERT_LIGHTNESS_EFFECT_GET_CLASS(obj) (G_TYPE_INSTANCE_GET_CLASS ((obj), SHELL_TYPE_INVERT_LIGHTNESS_EFFEC, ShellInvertLightnessEffectClass))
+
+#include "shell-invert-lightness-effect.h"
+
+#include <cogl/cogl.h>
+
+struct _ShellInvertLightnessEffect
+{
+ ClutterOffscreenEffect parent_instance;
+
+ CoglPipeline *pipeline;
+};
+
+struct _ShellInvertLightnessEffectClass
+{
+ ClutterOffscreenEffectClass parent_class;
+
+ CoglPipeline *base_pipeline;
+};
+
+/* Lightness inversion in GLSL.
+ */
+static const gchar *invert_lightness_source =
+ "cogl_texel = texture2D (cogl_sampler, cogl_tex_coord.st);\n"
+ "vec3 effect = vec3 (cogl_texel);\n"
+ "\n"
+ "float maxColor = max (cogl_texel.r, max (cogl_texel.g, cogl_texel.b));\n"
+ "float minColor = min (cogl_texel.r, min (cogl_texel.g, cogl_texel.b));\n"
+ "float lightness = (maxColor + minColor) / 2.0;\n"
+ "\n"
+ "float delta = (1.0 - lightness) - lightness;\n"
+ "effect.rgb = (effect.rgb + delta);\n"
+ "\n"
+ "cogl_texel = vec4 (effect, cogl_texel.a);\n";
+
+G_DEFINE_TYPE (ShellInvertLightnessEffect,
+ shell_invert_lightness_effect,
+ CLUTTER_TYPE_OFFSCREEN_EFFECT);
+
+static CoglPipeline *
+shell_glsl_effect_create_pipeline (ClutterOffscreenEffect *effect,
+ CoglTexture *texture)
+{
+ ShellInvertLightnessEffect *self = SHELL_INVERT_LIGHTNESS_EFFECT (effect);
+
+ cogl_pipeline_set_layer_texture (self->pipeline, 0, texture);
+
+ return cogl_object_ref (self->pipeline);
+}
+
+static void
+shell_invert_lightness_effect_dispose (GObject *gobject)
+{
+ ShellInvertLightnessEffect *self = SHELL_INVERT_LIGHTNESS_EFFECT (gobject);
+
+ if (self->pipeline != NULL)
+ {
+ cogl_object_unref (self->pipeline);
+ self->pipeline = NULL;
+ }
+
+ G_OBJECT_CLASS (shell_invert_lightness_effect_parent_class)->dispose (gobject);
+}
+
+static void
+shell_invert_lightness_effect_class_init (ShellInvertLightnessEffectClass *klass)
+{
+ GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
+ ClutterOffscreenEffectClass *offscreen_class;
+
+ offscreen_class = CLUTTER_OFFSCREEN_EFFECT_CLASS (klass);
+ offscreen_class->create_pipeline = shell_glsl_effect_create_pipeline;
+
+ gobject_class->dispose = shell_invert_lightness_effect_dispose;
+}
+
+static void
+shell_invert_lightness_effect_init (ShellInvertLightnessEffect *self)
+{
+ ShellInvertLightnessEffectClass *klass;
+ klass = SHELL_INVERT_LIGHTNESS_EFFECT_GET_CLASS (self);
+
+ if (G_UNLIKELY (klass->base_pipeline == NULL))
+ {
+ CoglSnippet *snippet;
+ CoglContext *ctx =
+ clutter_backend_get_cogl_context (clutter_get_default_backend ());
+
+ klass->base_pipeline = cogl_pipeline_new (ctx);
+
+ snippet = cogl_snippet_new (COGL_SNIPPET_HOOK_TEXTURE_LOOKUP,
+ NULL,
+ NULL);
+ cogl_snippet_set_replace (snippet, invert_lightness_source);
+ cogl_pipeline_add_layer_snippet (klass->base_pipeline, 0, snippet);
+ cogl_object_unref (snippet);
+
+ cogl_pipeline_set_layer_null_texture (klass->base_pipeline, 0);
+ }
+
+ self->pipeline = cogl_pipeline_copy (klass->base_pipeline);
+}
+
+/**
+ * shell_invert_lightness_effect_new:
+ *
+ * Creates a new #ShellInvertLightnessEffect to be used with
+ * clutter_actor_add_effect()
+ *
+ * Return value: (transfer full): the newly created
+ * #ShellInvertLightnessEffect or %NULL. Use g_object_unref() when done.
+ */
+ClutterEffect *
+shell_invert_lightness_effect_new (void)
+{
+ return g_object_new (SHELL_TYPE_INVERT_LIGHTNESS_EFFECT, NULL);
+}