LZ: Bitmaps

[Prev][Next][Index][Thread]

LZ: Bitmaps

>I am starting a new game and I need to learn how to use bitmaps.  For 
>example, I want to place an 16x20 bitmap
>of a happy face anywhere on the screen.  How would I do this?  I already 
>know that I really don't need nasr,
>since they won't actually be moving.


I would recommend that you make it so that the sprite will start exactly on 
the MSB of one byte and end on the LSB of the following byte.  This is so 
that the sprite covers only two bytes on the screen as opposed to 
coverering three of them and that's what NASR is for.  A basic routine to 
put a sprite on the screen would be:


	ld	hl,(PROGRAM_ADDR)
	ld	de,Sprite
	add	hl,de
	ex	de,hl		;de now points to Sprite
	ld	hl,$0000	;offset in video memory.  $0000 is upper left


Start:
	;input:  	hl=offset in video memory
	;	de=pointer to sprite
	ld	bc,VIDEO_MEM
	add	hl,bc			;hl now holds address of spot in video mem
	ld	b,2			;set to number of rows in sprite
Loop:
	push	bc
	ld	a,(de)
	ld	(hl),a
	inc	de
	inc	hl
	ld	a,(de)
	ld	(hl),a
	inc	de
	ld	bc,15
	add	hl,bc
	pop	bc
	djnz	Loop:
	ret




Sprite:
	.db	%10101010,%10011001
	.db	%10101010,%10011001


This routine SHOULD work.  I didn't bother to look through some of my 
programs to see if it's right, but it should be.  If it's not you should be 
able to fix the problem.  If not, then email me and I'll fix it for you.


Ed Plese, Jr.
(eplese@lnd.com)