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

As long as all values are in a range, let me say, less than 1000 and greater (or equal) than 0, which is common on colour values, do something like

int returnVal = (currPixel * newValue) / modifier

No need for doubles; it will even speed up the code. Needless to say, modifiershould not be zero.