How to copy a bitmap?

no-reply@allegro.cc (boulifb) — Wed, 31 May 2006 02:20:18 +0000

Hello guys,

I'd like to know how can I clone a bitmap that has been programmatically created?

1int main()
2{
allegro_init();
install_keyboard();
set_color_depth(32);
set_gfx_mode(GFX_AUTODETECT_WINDOWED, SCALE*160, SCALE*100, 0, 0);
7 
PLEVELDESC level=LoadLevel("level");
BITMAP* map=BuildMap(level);  // the map itself calculated 1 time
BITMAP* frame=NULL; // copy of the map
11 
while (!key[KEY_ESC])
{
  // how to do a fresh copy of the map without recalculate it???
  frame= CloneBitmap(map);  // reset the frame
  DrawOtherStuffs(frame);
  blit(frame, screen, 0, 0, 0, 0, SCREEN_W, SCREEN_H);
  destroy_bitmap(frame);
}

destroy_bitmap(map);
22 
remove_keyboard();
allegro_exit();
25 
return 0;
27}

How should I write the "CloneBitmap" function

I have seen nothing in the doc to do a bitmap copy...

Thanks for helping me.

Best regards.

Fred.

no-reply@allegro.cc (gnolam) — Wed, 31 May 2006 02:26:36 +0000

A bitmap copy is also known as a blit...

no-reply@allegro.cc (Onewing) — Wed, 31 May 2006 02:29:42 +0000

manual said:

The origin of the term "blit" is also rather interesting. This was originally BitBlt, an abbreviation of BITmap BLock Transfer, which was a function designed (possibly) by the people at Xerox who did so much of the pioneering work on graphics display systems, and subsequently copied by virtually everybody doing computer graphics (the Microsoft Windows GDI still provides a BitBlt function with identical functionality to the original). This routine was a workhorse for all sorts of drawing operations, basically copying bitmap graphics from one place to another, but including a number of different ROP modes (Raster OPerations) for doing things like XOR, inverting pixels, etc. A whole family of related words grew up around the BitBlt function, but "blt" is impossible to speak (try saying "bltter" or "bltting" :-) so people added the vowel to make it easier to pronounce.

Emphasis mine.

no-reply@allegro.cc (CursedTyrant) — Wed, 31 May 2006 02:32:10 +0000

My best shot would be:

1. Create a BITMAP.
2. Blit to it.
3. Return a pointer to the BITMAP.

Maybe:

BITMAP *CloneBitmap(BITMAP *BMP)
{
  BITMAP *Tmp = create_bitmap(BMP->width, BMP->height);
  blit(BMP, Tmp, 0, 0, 0, 0, BMP->width, BMP->height);
  return Tmp;
}

Now I might be wrong with the width and height, I can't remember their names, but I think the example should work.

no-reply@allegro.cc (Matthew Leverton) — Wed, 31 May 2006 03:07:06 +0000

It is w and h.

no-reply@allegro.cc (boulifb) — Wed, 31 May 2006 15:50:58 +0000

ah yes, blitting.... why should have not thought about it before...

many thanks

Fred.

1	int main()
2	{
3	allegro_init();
4	install_keyboard();
5	set_color_depth(32);
6	set_gfx_mode(GFX_AUTODETECT_WINDOWED, SCALE160, SCALE100, 0, 0);
7
8	PLEVELDESC level=LoadLevel("level");
9	BITMAP* map=BuildMap(level); // the map itself calculated 1 time
10	BITMAP* frame=NULL; // copy of the map
11
12	while (!key[KEY_ESC])
13	{
14	// how to do a fresh copy of the map without recalculate it???
15	frame= CloneBitmap(map); // reset the frame
16	DrawOtherStuffs(frame);
17	blit(frame, screen, 0, 0, 0, 0, SCREEN_W, SCREEN_H);
18	destroy_bitmap(frame);
19	}
20
21	destroy_bitmap(map);
22
23	remove_keyboard();
24	allegro_exit();
25
26	return 0;
27	}