GL_ARB_texture_swizzle http://www.opengl.org/registry/specs/ARB/texture_swizzle.txt GL_ARB_texture_swizzle GL_TEXTURE_SWIZZLE_R 0x8E42 GL_TEXTURE_SWIZZLE_G 0x8E43 GL_TEXTURE_SWIZZLE_B 0x8E44 GL_TEXTURE_SWIZZLE_A 0x8E45 GL_TEXTURE_SWIZZLE_RGBA 0x8E46