[boost] [gil] IMC4 Pixel format

Hey, I've been trying to find a definition for the IMC4<http://www.fourcc.org/yuv.php#IMC4>pixel format for GIL with no success, not even anything similar (planar pixel formats in which some of the channels are sub-sampled). I've spent many hours already trying to figure out how could I create such pixel format, and I am totally lost... The question is how can I specify that a pixel format is planar, and planes have different sizes due to sub-sampling!....I guess I'll have to override some operator[] operator++, operator-- Or to make a specialization of some classes. But how and where? planar_pixel_iterator? channel_iterator? I need some aid! please! Thanks is advance. H4rg.