Define my own convolutional kernel/mask/filter in Flux.jl

Hello all, I am trying to define my own convolutional kernels:
For 1D case:
[1 -2 1]
For 2D case:
| 0 1 0 |
| 1 -4 1 |
| 0 1 0 |
Does anyone have any idea on how to do that in Flux.jl?
You can only say how many kernels you want and how big are they, but I want to have these specific two.
I could use some other library, but I am now working with Flux.
Thank you!