The kernel will not only use all channels (different colors), but also use 4 values in one spatial dimension (e.g. values 0, 1, 2, 3).

Thanks so much. So, I have to use same weight for all position (position 0 to position 7). Is it right? Because my aim is find a linear combination of all vectors column by column. So, I expect to have different weights among columns. For example, (w00, w01,w02, w03) is for first column must be different with (w10, w11,w12, w13) of second column and so on. Is it possible?