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engines/ags/engine/gfx/blender.h

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+//=============================================================================
+//
+// AGS specific color blending routines for transparency and tinting effects
+//
+//=============================================================================
+
+#ifndef AGS_ENGINE_GFX_BLENDER_H
+#define AGS_ENGINE_GFX_BLENDER_H
+
+namespace AGS3 {
+
+//
+// Allegro's standard alpha blenders result in:
+// - src and dst RGB are combined proportionally to src alpha
+//   (src.rgb * src.alpha + dst.rgb * (1 - dst.alpha));
+// - final alpha is zero.
+// This blender is suggested for use with opaque destinations
+// (ones without alpha channel).
+//
+/* Declared in Allegro's color.h:
+void set_alpha_blender();
+*/
+
+// Customizable alpha blender that uses the supplied alpha value as src alpha,
+// and preserves destination's alpha channel (if there was one);
+void set_my_trans_blender(int r, int g, int b, int a);
+// Additive alpha blender plain copies src over, applying a summ of src and
+// dst alpha values.
+void set_additive_alpha_blender();
+// Opaque alpha blender plain copies src over, applying opaque alpha value.
+void set_opaque_alpha_blender();
+// Sets argb2argb for 32-bit mode, and provides appropriate funcs for blending 32-bit onto 15/16/24-bit destination
+void set_argb2any_blender();
+
+} // namespace AGS3
+
+#endif