Re: A86: Sprite XOR

To: assembly-86@lists.ticalc.org
Subject: Re: A86: Sprite XOR
From: Trent Lillehaugen <tllilleh@polymail.cpunix.calpoly.edu>
Date: Thu, 11 Sep 1997 17:20:07 -0700
References: <3.0.3.32.19970910223418.006af528@postoffice.worldnet.att.net> <3.0.3.32.19970911072939.006b0f90@postoffice.worldnet.att.net>
Reply-To: assembly-86@lists.ticalc.org

A. El-Helw wrote:

> So,  if I wanted to make an XOR routine, just add those three lines
> where I
> call the sprite ?  And is there anything else I have to do?

this is an optimizable code to XOR a sprite anywhere:
PutSpriteXOR: ; Puts a sprite stored at (HL) at B,C
      push bc           ; save BC
      push de           ; save DE
      push hl   ; save HL
      push hl   ; save HL
      ld e,b
      ld d,c
      call FindPixel ; NOTE i did not include the FindPixel Routine..
                           ;its the one found on this list earlier!
      ld de,$FC00  ; DE points to VID MEM
      ex de,hl                  ; DE = VID MEM + PIXEL LOC
      pop hl                    ; HL = PIC LOC
      ld b,(hl)                 ; get first byte from PIC LOC (width)
      inc hl                    ; HL = next byte in PIC LOCATION
      ld c,(hl)                 ; get second byte from PIC LOC (height)
      inc hl                    ; HL = START OF PIC
      push hl                   ; save HL
      pop ix   ; IX = START OF PIC
      ex de,hl                  ; HL = VID MEM + PIXEK LOC DE = START OF
PIC
PS_NewRow:
      push bc                   ; save BC
      ld d,(ix)   ; D = next byte of PIC
      inc ix   ; IX points to next byte
      push af                   ; save AF
      push hl   ; save HL
PS_NewCol:
      rl d   ; Rotate Left D
      ld e,a   ; e = a
      jr nc,PS_NoPixel        ; if No Carry then goto NoPixel
      ;************ can be OR or XOR or AND or whatever :)  *****
      xor (hl)                   ; a = a or (hl)
      ;***************************************************
      ld (hl),a                 ; hl = hl or a (basically)
      jr PS_NextPixel
PS_NoPixel:
      cpl
      and (hl)
      ld (hl),a
PS_NextPixel:
      ld a,e                    ; get A back
      rrca                      ; rotate right circular
      jr nc,PS_SameByte  ; if no carry then same byte
      inc hl                    ; else HL points to next byte in PIC
PS_SameByte:
      djnz PS_NewCol            ; go to next column
      pop hl
      pop af
      ld de,16
      add hl,de
      pop bc
      dec c
      jr nz,PS_NewRow
      pop hl
      pop de
      pop bc
      ret
this is just a modded version that I got from somwhere.. it's not my
code... (sorry to the author, i don't know who you are :(  )
--
Trent Lillehaugen
Computer Engineering Major
California Polytechnic University, San Luis Obispo
<tllilleh@polymail.calpoly.edu>

References:

A86: Sprite XOR

From: "A. El-Helw" <ahmed3@worldnet.att.net>

Re: A86: Sprite XOR

From: "A. El-Helw" <ahmed3@worldnet.att.net>