Okay
So far if you go to cpu_filters there are a bunch of files
You can look at EXAMPLE.cpp to see how to call a filter function
Right now there are:
blur
sharpen
emboss
edges
sobel
b_and_w (black and white)
Each can be called with:
cpu_blur("filename.bmp");
as seen in EXAMPLE.cpp
(include filters.h to make it work)

PS: compile with g++ (gcc doesnt work for some reason)