A pair of nested for loops

Listing 3 uses a pair of nested for loops to:

(This negated bitmap will later be copied to the screen bitmap producing the negated image in the bottom of Figure 1.)

Listing 3. Cycle through the bitmap negating each pixel. 
  for(int row = 0;row < 330;row++){
    for(int column = 0;column < 324;column++){
      pixel = getpixel(picA,column,row);
      red = getr(pixel);
      green = getg(pixel);
      blue = getb(pixel);
      putpixel(picA,column,row,makecol(
                             255-red,255-green,255-blue));
    }//end loop row
  }//end loop on column