I am given a matrix of integers with width w_g and height h_g filled with values 0 to w_g x h_g - 1 and a local matrix filter with width w_l and height h_l. I want to map each value in the matrix to a corresponding index in the smaller matrix.
For w_g = 9, h_g = 8, w_l = 3 and h_l = 2 the matrix values

would get mapped to the following indices:

I got this working with the following formula:

newValue = value % w_l + ((value / w_g) % h_l) * w_l

I’m currently searching for an adaption to this formula (or a new one) since this one fails when either w_g or h_g aren’t multiples of w_l corresponding h_l. The solution shouln’t consist of if-conditions etc. I am looking for a closed formula.

Thanks in advance.