exxfade.c from Allegro game programming library at Krugle

Show exxfade.c syntax highlighted

/*
 *    Example program for the Allegro library, by Shawn Hargreaves.
 *
 *    This program demonstrates how to load and display bitmap files
 *    in truecolor video modes, and how to crossfade between them.
 */


#include "allegro.h"



int show(char *name)
{
   AL_BITMAP *bmp, *buffer;
   AL_PALETTE pal;
   int alpha;

   /* load the file */
   bmp = al_load_bitmap(name, pal);
   if (!bmp)
      return -1;

   buffer = al_create_bitmap(AL_SCREEN_W, AL_SCREEN_H);
   al_blit(al_screen, buffer, 0, 0, 0, 0, AL_SCREEN_W, AL_SCREEN_H);

   al_set_palette(pal);

   /* fade it in on top of the previous picture */
   for (alpha=0; alpha<256; alpha+=8) {
      al_set_trans_blender(0, 0, 0, alpha);
      al_draw_trans_sprite(buffer, bmp, (AL_SCREEN_W-bmp->w)/2, (AL_SCREEN_H-bmp->h)/2);
      al_vsync();
      al_blit(buffer, al_screen, 0, 0, 0, 0, AL_SCREEN_W, AL_SCREEN_H);
      if (al_key_pressed()) {
	 al_destroy_bitmap(bmp);
	 al_destroy_bitmap(buffer);
	 if ((al_read_key() & 0xFF) == 27)
	    return 1;
	 else
	    return 0;
      }
   }

   al_blit(bmp, al_screen, 0, 0, (AL_SCREEN_W-bmp->w)/2, (AL_SCREEN_H-bmp->h)/2, bmp->w, bmp->h);

   al_destroy_bitmap(bmp);
   al_destroy_bitmap(buffer);

   if ((al_read_key() & 0xFF) == 27)
      return 1;
   else
      return 0;
}



int main(int argc, char *argv[])
{
   int i;

   allegro_init();

   if (argc < 2) {
      al_show_message("Usage: 'exxfade files.[bmp|lbm|pcx|tga]'\n");
      return 1;
   }

   al_install_keyboard(); 

   /* set the best color depth that we can find */
   al_set_color_depth(16);
   if (al_set_gfx_mode(AL_GFX_AUTODETECT, 640, 480, 0, 0) != 0) {
      al_set_color_depth(15);
      if (al_set_gfx_mode(AL_GFX_AUTODETECT, 640, 480, 0, 0) != 0) {
	 al_set_color_depth(32);
	 if (al_set_gfx_mode(AL_GFX_AUTODETECT, 640, 480, 0, 0) != 0) {
	    al_set_color_depth(24);
	    if (al_set_gfx_mode(AL_GFX_AUTODETECT, 640, 480, 0, 0) != 0) {
	       al_set_gfx_mode(AL_GFX_NONE, 0, 0, 0, 0);
	       al_show_message("Error setting graphics mode\n%s\n", al_error);
	       return 1;
	    }
	 }
      }
   }

   /* load all images in the same color depth as the display */
   al_set_color_conversion(AL_COLORCONV_TOTAL);

   /* process all the files on our command al_draw_line */
   for (i=1; i<argc; i++) {
      switch (show(argv[i])) {

	 case -1:
	    /* error */
	    al_set_gfx_mode(AL_GFX_NONE, 0, 0, 0, 0);
	    al_show_message("Error loading image file '%s'\n", argv[i]);
	    return 1;

	 case 0:
	    /* ok! */
	    break;

	 case 1:
	    /* quit */
	    al_remove_system();
	    return 0;
      }
   }

   return 0;
}

AL_END_OF_MAIN();
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