Added utility function imageSwizzleBGRA8 to convert RGBA8 image to BGRA8.

src/image.cpp

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2011-2013 Branimir Karadzic. All rights reserved.
+ * License: http://www.opensource.org/licenses/BSD-2-Clause
+ */
+
+#include <bx/float4_t.h>
+
+namespace bgfx
+{
+	static void imageSwizzleBGRA8Ref(uint8_t* _rgbaData, uint32_t _width, uint32_t _height) 
+	{
+		uint32_t dstpitch = _width*4;
+		for (uint32_t yy = 0; yy < _height; ++yy)
+		{
+			uint8_t* dst = &_rgbaData[yy*dstpitch];
+
+			for (uint32_t xx = 0; xx < _width; ++xx)
+			{
+				uint8_t tmp = dst[0];
+				dst[0] = dst[2];
+				dst[2] = tmp;
+				dst += 4;
+			}
+		}
+	}
+
+	void imageSwizzleBGRA8(uint8_t* _rgbaData, uint32_t _width, uint32_t _height)
+	{
+		if (0 != (_width&0xf)
+		||  _width < 16)
+		{
+			imageSwizzleBGRA8Ref(_rgbaData, _width, _height);
+			return;
+		}
+
+		uint32_t dstpitch = _width*4;
+		uint32_t num = dstpitch/16;
+
+		using namespace bx;
+
+		const float4_t mf0f0 = float4_isplat(0xff00ff00);
+		const float4_t m0f0f = float4_isplat(0x00ff00ff);
+
+		for (uint32_t yy = 0; yy < _height; ++yy)
+		{
+			uint8_t* ptr = &_rgbaData[yy*dstpitch];
+
+			for (uint32_t xx = 0; xx < num; ++xx)
+			{
+				const float4_t tabgr = float4_ld(ptr);
+				const float4_t t00ab = float4_srl(tabgr, 16);
+				const float4_t tgr00 = float4_sll(tabgr, 16);
+				const float4_t tgrab = float4_or(t00ab, tgr00);
+				const float4_t ta0g0 = float4_and(tabgr, mf0f0);
+				const float4_t t0g0b = float4_and(tgrab, m0f0f);
+				const float4_t targb = float4_or(ta0g0, t0g0b);
+				float4_st(ptr, targb);
+				ptr += 16;
+			}
+		}
+	}
+
+} // namespace bgfx