C++, my double or int value is always 0

Question

I\'m fairly new to C++ and I\'m experiencing some strange behaviour from a percentage increase method I am writing for some image editing software.

What I want to do is

Answer 1

casting to double should fix the error.

double returnVal =  (double ) (currPixel) / (modifier) * newValue;

see type casting rules typecasting rules in c.