A stained glass effect in C

Save this code to your computer with an appropriate name (such as glass.c) and download the glass images to go with it. Compile it with something like:

gcc -o glass glass.c -lbr -lm

and enjoy!

#include <stdio.h>
#include <stdlib.h>
#include <SDL/SDL.h>
#include <SDL/SDL_mixer.h>
#include <SDL/SDL_image.h>
#include <brick.h>


/* Compile with:  gcc -o glass glass.c -lm -lbr */


/*
 * a few configuration options
 */
#define SCREEN_W 256
#define SCREEN_H 180

#define DISPL_W 80
#define DISPL_H 100




int main() {

  int i,j;

  /* layer vars */
  int layer_id;

  /* the sprite variables */
  struct sprite *glass, *bear;

  /* the buffer for loading pngs, and a color key for the bear sprite */
  struct color key;

  /* a buffer to hold the pixel displacement data for the pane of glass */
  short displ[DISPL_H][DISPL_W][2];

  /* the bear sprite's position */
  int bx, by;

  /* a struct to contain inputs */
  struct input io;

  /* initialize brick and create the layer */
  init_brick();

  layer_id = layer_add();
  layer_set_sorting( layer_id, 1 );


  /*
   * now, we're going to create the stained glass effect by combining two sprites:
   * a color-adjustment sprite to give the glass some color, and a displacement
   * sprite to give it the fuzzy, mottled look.  first we'll create a
   * displacement map for the fuzzy effect, by making a list of small random
   * pixel displacement values, which will comprise the displacement sprite.
   */
  for( i=0; i < DISPL_H; i++ )
    for( j=0; j < DISPL_W; j++ ) {
      displ[i][j][0] = (random() & 7) - 3;
      displ[i][j][1] = (random() & 7) - 3;
    }

  /* and load the pane of glass */
  glass = sprite_create();
  sprite_add_frame(glass, frame_convert( frame_from_disk("window.png", NULL), FRAME_LT, NULL));
  sprite_add_subframe(glass, 0, frame_create(FRAME_DISPL, DISPL_W, DISPL_H, displ, NULL));

  /* position the sprite and add it to the list */
  sprite_set_position(glass, 100, 20);
  sprite_set_z_hint(glass, 10);
  list_add( layer_get_sprite_list(layer_id), glass);


  /*
   * and last, load the bear sprite, and set a color key to make
   * sure that the magenta background is made transparent
   */
  bear = sprite_create();
  key.r = 255;
  key.g = 0;
  key.b = 255;

  sprite_add_frame(bear, frame_copy(frame_from_disk("bear.png", &key)));
  list_add( layer_get_sprite_list(layer_id), bear);


  /* open the graphics display */
  graphics_open(GRAPHICS_ACCEL, SCREEN_W, SCREEN_H, 0, 3);


  /* initialize the sprite position and enter the main loop */
  bx = 0;
  by = 0;

  for(;;) {

    /* read the keyboard/joystick input */
    io_fetch(0, &io);

    /* update the sprite position */
    bx += io.hat[0].horiz;
    by += io.hat[0].vert;
    sprite_set_position(bear, bx, by);

    /* display the frame and run the delay loop */
    render_display();
    delay(50);

    /* quit on escape keypress */
    if( io.esc || io_has_quit() )
       {
	  quit_brick();
	  exit(0);
       }

  }

}