exblend.c from Allegro game programming library at Krugle

Show exblend.c syntax highlighted

/*
 *    Example program for the Allegro library, by Shawn Hargreaves.
 *
 *    This program demonstrates how to use the translucency functions in
 *    truecolor video modes.
 */


#include "allegro.h"



int main(int argc, char *argv[])
{
   char buf[256];
   AL_PALETTE pal;
   AL_BITMAP *image1;
   AL_BITMAP *image2;
   AL_BITMAP *buffer;
   int r, g, b, a;
   int x, y, w, h;
   int x1, y1, x2, y2;
   int prevx1, prevy1, prevx2, prevy2;
   int timer;
   int bpp = -1;
   int ret = -1;

   allegro_init(); 
   al_install_keyboard(); 
   al_install_timer();

   /* what color depth should we use? */
   if (argc > 1) {
      if ((argv[1][0] == '-') || (argv[1][0] == '/'))
	 argv[1]++;
      bpp = atoi(argv[1]);
      if ((bpp != 15) && (bpp != 16) && (bpp != 24) && (bpp != 32)) {
	 al_show_message("Invalid color depth '%s'\n", argv[1]);
	 return 1;
      }
   }

   if (bpp > 0) {
      /* set a user-requested color depth */
      al_set_color_depth(bpp);
      ret = al_set_gfx_mode(AL_GFX_AUTODETECT, 640, 480, 0, 0);
   }
   else {
      /* autodetect what color depths are available */
      static int color_depths[] = { 16, 15, 32, 24, 0 };
      for (a=0; color_depths[a]; a++) {
	 bpp = color_depths[a];
	 al_set_color_depth(bpp);
	 ret = al_set_gfx_mode(AL_GFX_AUTODETECT, 640, 480, 0, 0);
	 if (ret == 0)
	    break;
      }
   }

   /* did the video mode set properly? */
   if (ret != 0) {
      al_set_gfx_mode(AL_GFX_NONE, 0, 0, 0, 0);
      al_show_message("Error setting %d bit graphics mode\n%s\n", bpp, al_error);
      return 1;
   }

   /* specifiy that images should be loaded in a truecolor pixel format */
   al_set_color_conversion(AL_COLORCONV_TOTAL);

   /* load the first picture */
   al_replace_filename(buf, argv[0], "allegro.pcx", sizeof(buf));
   image1 = al_load_bitmap(buf, pal);
   if (!image1) {
      al_set_gfx_mode(AL_GFX_NONE, 0, 0, 0, 0);
      al_show_message("Error reading %s!\n", buf);
      return 1;
   }

   /* load the second picture */
   al_replace_filename(buf, argv[0], "mysha.pcx", sizeof(buf));
   image2 = al_load_bitmap(buf, pal);
   if (!image2) {
      al_destroy_bitmap(image1);
      al_set_gfx_mode(AL_GFX_NONE, 0, 0, 0, 0);
      al_show_message("Error reading %s!\n", buf);
      return 1;
   }

   /* create a double buffer bitmap */
   buffer = al_create_bitmap(AL_SCREEN_W, AL_SCREEN_H);

   /* Note that because we loaded the images as truecolor bitmaps, we don't
    * need to bother setting the palette, and we can display both on al_screen
    * at the same time even though the source files use two different 256
    * color palettes...
    */

   prevx1 = prevy1 = prevx2 = prevy2 = 0;

   al_printf_text(al_screen, al_font_8x8, 0, AL_SCREEN_H-8, al_make_color(255, 255, 255), "%d bpp", bpp);

   while (!al_key_pressed()) {
      timer = al_retrace_count;
      al_clear_bitmap(buffer);

      /* the first image moves in a slow al_draw_circle while being tinted to 
       * different colors...
       */
      x1= 160+al_fix_to_int(al_fix_sin(al_int_to_fix(timer)/16)*160);
      y1= 140-al_fix_to_int(al_fix_cos(al_int_to_fix(timer)/16)*140);
      r = 127-al_fix_to_int(al_fix_cos(al_int_to_fix(timer)/6)*127);
      g = 127-al_fix_to_int(al_fix_cos(al_int_to_fix(timer)/7)*127);
      b = 127-al_fix_to_int(al_fix_cos(al_int_to_fix(timer)/8)*127);
      a = 127-al_fix_to_int(al_fix_cos(al_int_to_fix(timer)/9)*127);
      al_set_trans_blender(r, g, b, 0);
      al_draw_lit_sprite(buffer, image1, x1, y1, a);
      al_printf_text(al_screen, al_font_8x8, 0, 0, al_make_color(r, g, b), "light: %d ", a);

      /* the second image moves in a faster al_draw_circle while the alpha value
       * fades in and out...
       */
      x2= 160+al_fix_to_int(al_fix_sin(al_int_to_fix(timer)/10)*160);
      y2= 140-al_fix_to_int(al_fix_cos(al_int_to_fix(timer)/10)*140);
      a = 127-al_fix_to_int(al_fix_cos(al_int_to_fix(timer)/4)*127);
      al_set_trans_blender(0, 0, 0, a);
      al_draw_trans_sprite(buffer, image2, x2, y2);
      al_printf_text(al_screen, al_font_8x8, 0, 8, al_make_color(a, a, a), "alpha: %d ", a);

      /* copy the double buffer across to the al_screen */
      al_vsync();

      x = MIN(x1, prevx1);
      y = MIN(y1, prevy1);
      w = MAX(x1, prevx1) + 320 - x;
      h = MAX(y1, prevy1) + 200 - y;
      al_blit(buffer, al_screen, x, y, x, y, w, h);

      x = MIN(x2, prevx2);
      y = MIN(y2, prevy2);
      w = MAX(x2, prevx2) + 320 - x;
      h = MAX(y2, prevy2) + 200 - y;
      al_blit(buffer, al_screen, x, y, x, y, w, h);

      prevx1 = x1;
      prevy1 = y1;
      prevx2 = x2;
      prevy2 = y2;
   }

   al_clear_keybuf();

   al_destroy_bitmap(image1);
   al_destroy_bitmap(image2);
   al_destroy_bitmap(buffer);

   return 0;
}

AL_END_OF_MAIN();
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