From:	dragun AT my-dejanews DOT com
Newsgroups:	comp.os.msdos.djgpp
Subject:	Why doesnt this lighting work right in Allegro?
Date:	Tue, 22 Sep 1998 02:05:06 GMT
Organization:	Deja News - The Leader in Internet Discussion
Lines:	142
Message-ID:	<6u70ki$d34$1@nnrp1.dejanews.com>
NNTP-Posting-Host:	168.191.156.93
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

I coded this in Allegro (I'm using C++):

//// INCLUDE

#include <iostream.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <conio.h>
#include <time.h>
#include "allegro.h"
#include "game.hpp"


//// DEFINE

#define tilSIZE    32
#define maxLEVS     3
#define maxCOLS   100
#define maxROWS   100
#define maxTILE   144


//// STRUCTURES

typedef struct
{
 unsigned char img;
} tileMAP;


//// GLOBALS

BITMAP *buffer;
DATAFILE *game_dat, *exec_dat, *base_dat, *mask_dat, *objt_dat;
COLOR_MAP *clr_map, *lit_map, *trn_map, *drk_map;

char map_name[80];

int mapX, mapY, DONE;
float tileX, tileY;
float speed = 1, sped = 4;
tileMAP levelMAP[maxLEVS][maxCOLS][maxROWS];


//// FUNCTION PROTOTYPES

void LoadMap(void);
void DrawMap(int x, int y);
void Bounds(void);


//// FUNCTIONS

RGB add_blender(PALETTE pal, int x, int y)
{
   RGB rgb;
   int r, g, b;

   r = (int)pal[x].r + (int)pal[y].r;
   g = (int)pal[x].g + (int)pal[y].g;
   b = (int)pal[x].b + (int)pal[y].b;

   rgb.r = MIN(r, 63);
   rgb.g = MIN(g, 63);
   rgb.b = MIN(b, 63);

   return rgb;
}

//// MAIN

main()
{
 allegro_init();
 set_gfx_mode(GFX_AUTODETECT, 640, 480, 0, 0);
 install_keyboard();
 install_mouse();
 install_timer();
 exec_dat = load_datafile("exec.dat");
 game_dat = load_datafile("game.dat");
 base_dat = load_datafile("base.dat");
 mask_dat = load_datafile("mask.dat");
 objt_dat = load_datafile("objt.dat");

 if (!game_dat || !base_dat || !mask_dat || !objt_dat)
  {
   allegro_exit();
   exit(1);
  }


 set_pallete(game_dat[2].dat);
 buffer = create_bitmap(640, 480);
 clear(buffer);

 rgb_map = new RGB_MAP;
 create_rgb_table(rgb_map, (RGB *)game_dat[2].dat, NULL);

 clr_map = new COLOR_MAP;
 create_color_table(clr_map, (RGB *)game_dat[2].dat, add_blender, NULL);

 lit_map = new COLOR_MAP;
 create_light_table(lit_map, (RGB *)game_dat[2].dat, 64, 64, 64, NULL);

 drk_map = new COLOR_MAP;
 create_light_table(drk_map, (RGB *)game_dat[2].dat, 0, 0, 0, NULL);

 trn_map = new COLOR_MAP;
 create_trans_table(trn_map, (RGB *)game_dat[2].dat, 128, 128, 128, NULL);

 color_map = lit_map;

   drawing_mode(DRAW_MODE_TRANS, NULL, 0, 0);
   color_map = drk_map;
   draw_trans_sprite(buffer, exec_dat[2].dat, 228, 216);
   drawing_mode(DRAW_MODE_SOLID, NULL, 0, 0);
   draw_sprite(buffer, exec_dat[1].dat, 224, 212);
   blit(exec_dat[3].dat, buffer, 0, 0, 480, 0, 160, 480);
   vsync();
   blit(buffer, screen, 0, 0, 0, 0, 640, 480);

 unload_datafile(game_dat);
 unload_datafile(base_dat);
 unload_datafile(mask_dat);
 unload_datafile(objt_dat);
 destroy_bitmap(buffer);
 allegro_exit();
 exit(0);
}

whenever I blit a transparent image with draw_trans_sprite(), I have to set
the background color that's suppose to be masked (originally 0) to 255
because that sets the transparent function to do a small tranparency. I want
it to do a normal masked blitting WITH the transparency effect. Any ideas on
how to do this?

Note that most of the functions to do the transparency is ripped off from the
lighting demo on Allegro's homepage.

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