Beginning of the program named ImageNegate01

Listing 1 shows the beginning of the program.

Listing 1 includes the declaration and initialization of four local variables.

There's nothing new here, but a few comments are in order.

Listing 1. Beginning of the program named ImageNegate01. 
#include 

int main(){
  int pixel = 0;//temporary storage for a pixel
  
  //Temporary storage for red, green, and blue values
  int red = 0;
  int green = 0;
  int blue = 0;

  //Typical Allegro setup.
  allegro_init();
  install_keyboard();
  set_color_depth(32);

  set_gfx_mode(GFX_AUTODETECT_WINDOWED,324,660,0,0);