From 2edfcf08707c3627b6b27289ba607a7183d63b01 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Mon, 1 Feb 2021 21:18:29 +0200
Subject: [PATCH] Support BGR and BGRA as texture formats through swizzling

---
 source/pixelformat.cpp | 22 +++++++++++++++++++++-
 source/pixelformat.h   |  4 ++++
 source/texture.cpp     | 13 +++++++++++--
 source/texture.h       |  3 ++-
 4 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/source/pixelformat.cpp b/source/pixelformat.cpp
index cc6a6d00..94bf9716 100644
--- a/source/pixelformat.cpp
+++ b/source/pixelformat.cpp
@@ -64,6 +64,10 @@ void operator>>(const LexicalConverter &conv, PixelFormat &fmt)
 		fmt = SRGB8;
 	else if(conv.get()=="SRGB8_ALPHA8")
 		fmt = SRGB8_ALPHA8;
+	else if(conv.get()=="BGR8")
+		fmt = BGR8;
+	else if(conv.get()=="BGRA8")
+		fmt = BGRA8;
 	else if(conv.get()=="LUMINANCE8")
 		fmt = LUMINANCE8;
 	else if(conv.get()=="LUMINANCE8_ALPHA8")
@@ -127,7 +131,7 @@ PixelFormat pixelformat_from_image(const Graphics::Image &image)
 
 PixelFormat make_pixelformat(PixelComponents comp, DataType type, bool srgb)
 {
-	if(srgb && type!=UNSIGNED_BYTE && comp!=RGB && comp!=RGBA)
+	if(srgb && type!=UNSIGNED_BYTE && comp!=RGB && comp!=RGBA && comp!=BGR && comp!=BGRA)
 		throw invalid_argument("make_pixelformat");
 
 	switch(comp)
@@ -164,6 +168,14 @@ PixelFormat make_pixelformat(PixelComponents comp, DataType type, bool srgb)
 		case FLOAT: return RGBA32F;
 		default: throw invalid_argument("make_pixelformat");
 		}
+	case BGR:
+		if(type!=UNSIGNED_BYTE)
+			throw invalid_argument("make_pixelformat");
+		return (srgb ? BGR8 : SBGR8);
+	case BGRA:
+		if(type!=UNSIGNED_BYTE)
+			throw invalid_argument("make_pixelformat");
+		return (srgb ? BGRA8 : SBGR8_ALPHA8);
 	case LUMINANCE:
 		if(type!=UNSIGNED_BYTE)
 			throw invalid_argument("make_pixelformat");
@@ -217,6 +229,10 @@ PixelComponents get_components(PixelFormat pf)
 	case RGBA16F:
 	case RGBA32F:
 	case SRGB8_ALPHA8: return RGBA;
+	case BGR8:
+	case SBGR8: return BGR;
+	case BGRA8:
+	case SBGR8_ALPHA8: return BGRA;
 	case LUMINANCE8: return LUMINANCE;
 	case LUMINANCE8_ALPHA8: return LUMINANCE_ALPHA;
 	case STENCIL_INDEX8: return STENCIL_INDEX;
@@ -284,6 +300,10 @@ DataType get_component_type(PixelFormat pf)
 	case RGBA8:
 	case SRGB8:
 	case SRGB8_ALPHA8:
+	case BGR8:
+	case BGRA8:
+	case SBGR8:
+	case SBGR8_ALPHA8:
 	case LUMINANCE8:
 	case LUMINANCE8_ALPHA8:
 		return UNSIGNED_BYTE;
diff --git a/source/pixelformat.h b/source/pixelformat.h
index 9dec8234..96f859ca 100644
--- a/source/pixelformat.h
+++ b/source/pixelformat.h
@@ -49,6 +49,10 @@ enum PixelFormat
 	RGBA32F         = GL_RGBA32F,
 	SRGB8           = GL_SRGB8,
 	SRGB8_ALPHA8    = GL_SRGB8_ALPHA8,
+	BGR8            = 200000,
+	BGRA8           = 200001,
+	SBGR8           = 200002,
+	SBGR8_ALPHA8    = 200003,
 	LUMINANCE8      = GL_LUMINANCE8,
 	LUMINANCE8_ALPHA8 = GL_LUMINANCE8_ALPHA8,
 	DEPTH_COMPONENT16 = GL_DEPTH_COMPONENT16,
diff --git a/source/texture.cpp b/source/texture.cpp
index f0c55999..cf32ca30 100644
--- a/source/texture.cpp
+++ b/source/texture.cpp
@@ -18,7 +18,8 @@ int Texture::swizzle_orders[] =
 {
 	GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA,
 	GL_RED, GL_RED, GL_RED, GL_ONE,
-	GL_RED, GL_RED, GL_RED, GL_GREEN
+	GL_RED, GL_RED, GL_RED, GL_GREEN,
+	GL_BLUE, GL_GREEN, GL_RED, GL_ALPHA
 };
 
 Texture::Texture(GLenum t, ResourceManager *m):
@@ -60,6 +61,14 @@ void Texture::set_internal_format(PixelFormat fmt)
 		comp = RG;
 		swiz = RG_TO_LUMINANCE_ALPHA;
 		break;
+	case BGR:
+		comp = RGB;
+		swiz = RGB_TO_BGR;
+		break;
+	case BGRA:
+		comp = RGBA;
+		swiz = RGB_TO_BGR;
+		break;
 	default:;
 	}
 
@@ -73,7 +82,7 @@ void Texture::set_internal_format(PixelFormat fmt)
 
 PixelComponents Texture::get_upload_components(PixelComponents comp) const
 {
-	if(comp==LUMINANCE || comp==LUMINANCE_ALPHA)
+	if(comp==LUMINANCE || comp==LUMINANCE_ALPHA || comp==BGR || comp==BGRA)
 		return get_components(ifmt);
 	else
 		return comp;
diff --git a/source/texture.h b/source/texture.h
index 71192fef..6c0fbf25 100644
--- a/source/texture.h
+++ b/source/texture.h
@@ -64,7 +64,8 @@ protected:
 	{
 		NO_SWIZZLE,
 		R_TO_LUMINANCE,
-		RG_TO_LUMINANCE_ALPHA
+		RG_TO_LUMINANCE_ALPHA,
+		RGB_TO_BGR
 	};
 
 	unsigned id;
-- 
2.43.0