Added subtractive and multiplicative blend modes (thanks vrld)

src/modules/graphics/Graphics.cpp

@@ -1,14 +1,14 @@
 /**
 * Copyright (c) 2006-2010 LOVE Development Team
-* 
+*
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
-* 
+*
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
-* 
+*
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
@@ -88,7 +88,7 @@ namespace graphics
 		return pointStyles.find(in, out);
 	}
 
-	StringMap<Graphics::DrawMode, Graphics::DRAW_MAX_ENUM>::Entry Graphics::drawModeEntries[] = 
+	StringMap<Graphics::DrawMode, Graphics::DRAW_MAX_ENUM>::Entry Graphics::drawModeEntries[] =
 	{
 		{ "line", Graphics::DRAW_LINE },
 		{ "fill", Graphics::DRAW_FILL },
@@ -96,7 +96,7 @@ namespace graphics
 
 	StringMap<Graphics::DrawMode, Graphics::DRAW_MAX_ENUM> Graphics::drawModes(Graphics::drawModeEntries, sizeof(Graphics::drawModeEntries));
 
-	StringMap<Graphics::AlignMode, Graphics::ALIGN_MAX_ENUM>::Entry Graphics::alignModeEntries[] = 
+	StringMap<Graphics::AlignMode, Graphics::ALIGN_MAX_ENUM>::Entry Graphics::alignModeEntries[] =
 	{
 		{ "left", Graphics::ALIGN_LEFT },
 		{ "right", Graphics::ALIGN_RIGHT },
@@ -105,15 +105,17 @@ namespace graphics
 
 	StringMap<Graphics::AlignMode, Graphics::ALIGN_MAX_ENUM> Graphics::alignModes(Graphics::alignModeEntries, sizeof(Graphics::alignModeEntries));
 
-	StringMap<Graphics::BlendMode, Graphics::BLEND_MAX_ENUM>::Entry Graphics::blendModeEntries[] = 
+	StringMap<Graphics::BlendMode, Graphics::BLEND_MAX_ENUM>::Entry Graphics::blendModeEntries[] =
 	{
 		{ "alpha", Graphics::BLEND_ALPHA },
 		{ "additive", Graphics::BLEND_ADDITIVE },
+		{ "subtractive", Graphics::BLEND_SUBTRACTIVE },
+		{ "multiplicative", Graphics::BLEND_MULTIPLICATIVE },
 	};
 
 	StringMap<Graphics::BlendMode, Graphics::BLEND_MAX_ENUM> Graphics::blendModes(Graphics::blendModeEntries, sizeof(Graphics::blendModeEntries));
 
-	StringMap<Graphics::ColorMode, Graphics::COLOR_MAX_ENUM>::Entry Graphics::colorModeEntries[] = 
+	StringMap<Graphics::ColorMode, Graphics::COLOR_MAX_ENUM>::Entry Graphics::colorModeEntries[] =
 	{
 		{ "replace", Graphics::COLOR_REPLACE },
 		{ "modulate", Graphics::COLOR_MODULATE },
@@ -121,7 +123,7 @@ namespace graphics
 
 	StringMap<Graphics::ColorMode, Graphics::COLOR_MAX_ENUM> Graphics::colorModes(Graphics::colorModeEntries, sizeof(Graphics::colorModeEntries));
 
-	StringMap<Graphics::LineStyle, Graphics::LINE_MAX_ENUM>::Entry Graphics::lineStyleEntries[] = 
+	StringMap<Graphics::LineStyle, Graphics::LINE_MAX_ENUM>::Entry Graphics::lineStyleEntries[] =
 	{
 		{ "smooth", Graphics::LINE_SMOOTH },
 		{ "rough", Graphics::LINE_ROUGH }
@@ -129,7 +131,7 @@ namespace graphics
 
 	StringMap<Graphics::LineStyle, Graphics::LINE_MAX_ENUM> Graphics::lineStyles(Graphics::lineStyleEntries, sizeof(Graphics::lineStyleEntries));
 
-	StringMap<Graphics::PointStyle, Graphics::POINT_MAX_ENUM>::Entry Graphics::pointStyleEntries[] = 
+	StringMap<Graphics::PointStyle, Graphics::POINT_MAX_ENUM>::Entry Graphics::pointStyleEntries[] =
 	{
 		{ "smooth", Graphics::POINT_SMOOTH },
 		{ "rough", Graphics::POINT_ROUGH }

src/modules/graphics/Graphics.h

@@ -1,14 +1,14 @@
 /**
 * Copyright (c) 2006-2010 LOVE Development Team
-* 
+*
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
-* 
+*
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
-* 
+*
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
@@ -35,36 +35,38 @@ namespace graphics
 
 		enum DrawMode
 		{
-			DRAW_LINE = 1, 
+			DRAW_LINE = 1,
 			DRAW_FILL,
 			DRAW_MAX_ENUM
 		};
 
 		enum AlignMode
 		{
-			ALIGN_LEFT = 1, 
+			ALIGN_LEFT = 1,
-			ALIGN_CENTER, 
+			ALIGN_CENTER,
 			ALIGN_RIGHT,
 			ALIGN_MAX_ENUM
 		};
 
 		enum BlendMode
 		{
-			BLEND_ALPHA = 1, 
+			BLEND_ALPHA = 1,
 			BLEND_ADDITIVE,
+			BLEND_SUBTRACTIVE,
+			BLEND_MULTIPLICATIVE,
 			BLEND_MAX_ENUM
 		};
 
 		enum ColorMode
 		{
-			COLOR_MODULATE = 1, 
+			COLOR_MODULATE = 1,
 			COLOR_REPLACE,
 			COLOR_MAX_ENUM
 		};
 
 		enum LineStyle
 		{
-			LINE_ROUGH = 1, 
+			LINE_ROUGH = 1,
 			LINE_SMOOTH,
 			LINE_MAX_ENUM
 		};

src/modules/graphics/opengl/Graphics.cpp

@@ -533,10 +533,19 @@ namespace opengl
 
 	void Graphics::setBlendMode( Graphics::BlendMode mode )
 	{
-		if(mode == BLEND_ADDITIVE)
+		glAlphaFunc(GL_GEQUAL, 0);
-			glBlendFunc(GL_SRC_ALPHA, GL_ONE);
+
-		else // mode == BLEND_ALPHA
+		if (mode == BLEND_SUBTRACTIVE)
+			glBlendEquation(GL_FUNC_REVERSE_SUBTRACT);
+		else
+			glBlendEquation(GL_FUNC_ADD);
+
+		if (mode == BLEND_ALPHA)
 			glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+		else if (mode == BLEND_MULTIPLICATIVE)
+			glBlendFunc(GL_DST_COLOR, GL_ONE_MINUS_SRC_ALPHA);
+		else
+			glBlendFunc(GL_SRC_ALPHA, GL_ONE);
 	}
 
 	void Graphics::setColorMode ( Graphics::ColorMode mode )