COGLES2Driver: fix swapped color screenshots.

Thanks @sfan5 for patch (05c109a1d5)
Forum: https://irrlicht.sourceforge.io/forum/viewtopic.php?f=2&t=52819&p=306518


git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/branches/ogl-es@6383 dfc29bdd-3216-0410-991c-e03cc46cb475

changes.txt

@@ -1,6 +1,7 @@
 --------------------------
 Changes in ogl-es (not yet released - will be merged with trunk at some point)
 
+- COGLES2Driver: fix swapped color screenshots. Thanks @sfan5 for patch (https://github.com/minetest/irrlicht/commit/05c109a1d52db8293d8721337853043924feedae)
 - Add support for (experimental) WebGL1 driver for emscripten (still work in process)
 - Add support for emscripten. Thanks @labsin for the patch.
 - Add IVideoDriver::getAmbientLight function so shaders can access global ambient light easier

source/Irrlicht/COGLES2Driver.cpp

@@ -2535,7 +2535,7 @@ COGLES2Driver::~COGLES2Driver()
 		if (target==video::ERT_MULTI_RENDER_TEXTURES || target==video::ERT_RENDER_TEXTURE || target==video::ERT_STEREO_BOTH_BUFFERS)
 			return 0;
 
-		GLint internalformat = GL_RGBA;
+		GLint internalformat = GL_RGBA;	// Note BGRA not available on ES2. Thought there might be extensions we could use maybe.
 		GLint type = GL_UNSIGNED_BYTE;
 		{
 //			glGetIntegerv(GL_IMPLEMENTATION_COLOR_READ_FORMAT, &internalformat);
@@ -2591,6 +2591,22 @@ COGLES2Driver::~COGLES2Driver()
 		}
 		delete [] tmpBuffer;
 
+		// also GL_RGBA doesn't match the internal encoding of the image (which is BGRA)
+		if (GL_RGBA == internalformat && GL_UNSIGNED_BYTE == type)
+		{
+			pixels = static_cast<u8*>(newImage->getData());
+			for (u32 i = 0; i < ScreenSize.Height; i++)
+			{
+				for (u32 j = 0; j < ScreenSize.Width; j++)
+				{
+					u32 c = *(u32*) (pixels + 4 * j);
+					*(u32*) (pixels + 4 * j) = (c & 0xFF00FF00) |
+						((c & 0x00FF0000) >> 16) | ((c & 0x000000FF) << 16);
+				}
+				pixels += pitch;
+			}
+		}
+
 		if (testGLError(__LINE__))
 		{
 			newImage->drop();