question about variables of type double and NIOS2?

good afternoon,

to transform a variable from double to integer i multiply each number by pow(2,P) and i just take the integer part.

here "P" is variable from 8 ,16,32.

i began by testing the 2D convolution using fixed-point.

i declared my variables as integer but i have been encountered two problems:

1-first :a null coefficients if i take a low value of P (P=8).

for example i have this two coefficients:-0,00221819585464577,-0,00877313479158837 that i want to transform it to integer

if i multiply (-0,00221819585464577)*pow(2,8) and i take the integer part i will have zero as coefficient. it's a problem.

2-secand :an overflow in my algorithm if i take P=16:

if i multiply (-0,00221819585464577) by pow(2,16) i will have an overflow.so a bad result.

please how can i do to solve this problem (to implement this algorithm an hardware).

thanks an advance