Halp me /prog/ramming experts

So I'm working with uncompressed images in C++...
Can anyone write a piece of pseudo code to demonstrate how a horizontal Sobel filter or vertical sobel filter is supposed to work?

for x ← 0 to width
    for y ← 0 to height
        dest[x,y] = src[x-1,y-1] + 2 * src[x,y-1] + src[x+1,y-1] - src[x-1,y+1] - 2 * src[x,y+1] - src[x+1,y+1]