GL_EXT_texture_compression_s3tc http://www.opengl.org/registry/specs/gl/EXT/texture_compression_s3tc.txt GL_EXT_texture_compression_s3tc GL_COMPRESSED_RGB_S3TC_DXT1_EXT 0x83F0 GL_COMPRESSED_RGBA_S3TC_DXT1_EXT 0x83F1 GL_COMPRESSED_RGBA_S3TC_DXT3_EXT 0x83F2 GL_COMPRESSED_RGBA_S3TC_DXT5_EXT 0x83F3