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improved format and ASM decompressor
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(image width stored in data file, ASM decompressor is now IRQ and VRAM
*safe*
- also: official name is now "ShrunkTileMap")
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@sverx
sverx committed Dec 28, 2017
1 parent a1c72c9 commit e4bedc1
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2 changes: 1 addition & 1 deletion README.md
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@@ -1,4 +1,4 @@
STMcomp
=====================

Sverx's TileMap compressed format Bmp2Tile plugin and Z80 decompression routine
ShrunkTileMap compressed format Bmp2Tile plugin and Z80 decompression routine
Binary file modified compressor plugin/gfxcomp_stm.dll
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8 changes: 7 additions & 1 deletion compressor plugin/src/gfxcomp_stm.c
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Expand Up @@ -82,7 +82,7 @@ bool checkHI (int i) {
}

__declspec(dllexport) const char* getName() {
return "Sverx`s TileMap";
return "ShrunkTileMap (compressed)";
}

__declspec(dllexport) const char* getExt() {
Expand All @@ -104,6 +104,12 @@ __declspec(dllexport) int compressTilemap(uint8_t* source, uint32_t width, uint3
cur_HH=0;
writepos=0;

// write header (it's just 1 byte and it stores the width -in tiles- of the map
if (writepos<outsize)
outbuf[writepos++]=width; // write map width in tiles
else
return (0); // please give me more space for output

while (current<in_size) {

// check if the HH part of the next tile is the same as what we have
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240 changes: 167 additions & 73 deletions decompressor/src/STM_tilemap_decomp.inc
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@@ -1,80 +1,174 @@
; ***** Sverx's TileMap decompressor *****
; ***** ShrunkTileMap (previously known as "Sverx's TileMap") decompressor *****
; ***** by sverx - https://github.com/sverx/STMcomp/tree/master/decompressor/src *****
; ***** (now VRAM / Interrupt *SAFE* !!!) *****
; ***** (note: code backported from devkitSMS) *****

; to use it, you have to do this:
; ld hl,compressed_tilemap ; - set source address
; ld de,VRAMAddress|$4000 ; - set destination VRAM address, ORed with $4000
; ************************************************************************************
; to use this function, you have to do this:
; ld hl,STMcompr_tilemap ; load address of STM data into HL
; ld de,VRAMAddress ; set destination VRAM address into DE
; call STM_tilemap_decompr
; the function needs 9 bytes of RAM to work, see ramsection at the end of this file
; ************************************************************************************

.section "Sverx's TileMap decompressor" free
; HL = compressed tilemap binary (source)
; DE = VRAM address (destination) - ORed with $4000
; destroys AF,BC,DE,HL,IX
.section "ShortTileMap decompressor" free
; HL = compressed tilemap (source)
; DE = VRAM address (destination)
; destroys AF,BC,DE,HL
STM_tilemap_decompr:
ld c,$bf ; set VRAM address
out (c),e
out (c),d
ld c,$be ; set C to VDP data port
ld d,$00 ; sets HH to $00
ld ix,$0000 ; sets oldHH/flags to $0000
_MainLoop:
ld a,ixl ; do we need to restore HH?
or a
jr z,+ ; if flag is 0 then no restore
ld d,ixh ; restore HH
ld ixl,$0 ; reset restore flag
_MainLoop_nocheck:
+:ld a,(hl)
inc hl
rra ; is it a RLE run?
jr c,_RLE
rra ; is a RAW run?
jr nc,_RAW

; set new HH
rra ; is it a temporary set?
jr nc,_noTemp
ld ixh,d ; save old HH
ld ixl,$1 ; raise restore flag
_noTemp:
and $1F ; keep only last 5 bits
ld d,a ; set new HH
jp _MainLoop_nocheck

_RLE:
rra ; is it a RLE run of same value bytes?
jr c,_incrementalRLE
and $3F ; keep only last 6 bits (counter)
add a,2 ; counter +=2
ld b,a
ld e,(hl) ; load value
inc hl
-:out (c),e ; push (same) values to VRAM
out (c),d
djnz -
jp _MainLoop

_RAW:
and $3F ; keep only last 6 bits (counter)
ret z ; if counter==0 then data is over, leave!
ld b,a
-:ld e,(hl) ; load value
inc hl
out (c),e ; push value to VRAM
out (c),d
djnz -
jp _MainLoop
ld a,$40
or d
ld d,a
ld (STM_dest),de
xor a
ld (STM_HH),a
ld (STM_oldHH),a
ld (STM_needRestore),a
ld a,(hl)
ld (STM_width),a
ld (STM_ttw),a
inc hl
ld (STM_src),hl
ld hl,(STM_dest)
ld c, $BF ; set VDP Control Port
di ; make it interrupt SAFE
out (c),l
out (c),h
ei
_STM_loop:
ld hl,(STM_src)
ld a,(hl)
inc hl
ld (STM_src),hl
rra
jr nc,_STM_noRLE
rra
jr nc,_STM_RLE
; ***************** RLE of successive words
and $3F ; keep only last 6 bits (counter)
add a,$02
ld b,a ; b = cnt
ld a,(STM_HH)
ld d,a ; d = high part of tile
ld e,(hl) ; e = low part of tile
inc hl
ld (STM_src),hl ; src++
ld hl,STM_ttw
ld c,(hl) ; c = ttw
_STM_inc_RLE_loop:
ld a,e ; write tile to VRAM respecting access time costraints
out ($BE),a ; 11
ld a,d ; 4
sub $00 ; *delay* 7
dec c ; ttw-- 4 = 26 (VRAM SAFE)
out ($BE),a
call z,_STM_setAddr ; ttw==0?
dec b
jr z,_STM_inc_RLE_done ; cnt==0?
inc de ; tile++
jr _STM_inc_RLE_loop
_STM_inc_RLE_done:
ld hl,STM_HH ; save high part of tile
ld (hl),d
ld hl,STM_ttw ; save ttw
ld (hl),c
_STM_check_restore:
ld a,(STM_needRestore)
or a
jr z,_STM_loop
xor a
ld (STM_needRestore),a
ld a,(STM_oldHH)
ld (STM_HH),a
jr _STM_loop
_STM_noRLE:
rra
jr nc,_STM_RAW
; ***************** special
rra
jr nc,_STM_no_temp_HH
ld b,a
ld a,(STM_HH)
ld (STM_oldHH),a
ld a,$01
ld (STM_needRestore),a
ld a,b
_STM_no_temp_HH:
and $1F ; keep only last 5 bits
ld (STM_HH),a
jr _STM_loop
_STM_RLE:
; ***************** RLE
and $3F ; keep only last 6 bits (counter)
add a,$02
ld b,a ; b = cnt
ld a,(STM_HH)
ld d,a ; d = high part of tile
ld e,(hl) ; e = low part of tile
inc hl
ld (STM_src),hl ; src++
ld hl,STM_ttw
ld c,(hl) ; c = ttw
_STM_RLE_loop:
ld a,e ; write tile to VRAM respecting access time costraints
out ($BE),a ; 11
ld a,d ; 4
sub $00 ; *delay* 7
dec c ; ttw-- 4 = 26 (VRAM SAFE)
out ($BE),a
call z,_STM_setAddr ; ttw==0?
dec b
jr nz,_STM_RLE_loop ; cnt==0?
ld hl,STM_ttw ; save ttw
ld (hl),c
jr _STM_check_restore
_STM_RAW:
; ***************** RAW
and $3F ; keep only last 6 bits (counter)
or a
ret z ; if cnt is 0 - end of STM
ld b,a ; b = cnt
ld hl,STM_ttw
ld c,(hl) ; c = ttw
_STM_RAW_loop:
ld hl,(STM_src)
ld a,(hl)
out ($BE),a ; 11 low part of tile
inc hl ; 6
ld (STM_src),hl ; 16 src++
ld a,(STM_HH) ; 13 high part of tile
out ($BE),a ; xx = VRAM safe
dec c
call z,_STM_setAddr
dec b
jr nz,_STM_RAW_loop
ld hl,STM_ttw
ld (hl),c
jr _STM_check_restore
_STM_setAddr:
ld hl,(STM_dest)
ld a,b ; preserve b
ld bc,64
add hl,bc
ld b,a ; restore b
ld (STM_dest),hl
ld c,$BF ; set VDP Control Port
di ; make it interrupt SAFE
out (c),l
out (c),h
ei
ld a,(STM_width)
ld (STM_ttw),a
ld c,a
ret
.ends

_incrementalRLE:
and $3F ; keep only last 6 bits (counter)
add a,2 ; counter +=2
ld b,a
ld e,(hl) ; load start value
inc hl
-:out (c),e ; push incremental values to VRAM
out (c),d
inc de
djnz -
dec de ; this is to keep HH consistent with last value
jp _MainLoop
.ramsection "STM variables" slot 3
STM_src dw
STM_dest dw
STM_HH db
STM_oldHH db
STM_needRestore db
STM_ttw db
STM_width db
.ends
12 changes: 8 additions & 4 deletions file format.txt
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@@ -1,8 +1,12 @@
Format details (everything is stored as run of bytes)
Format details:

first byte -- other bytes that may be following
%nnnnnn01 -- dd : run of n+2 (2 to 65) same word value HHdd (a.k.a. "normal" RLE)
%nnnnnn11 -- dd : run of n+2 (2 to 65) successive word values (HHdd, HHdd+1, HHdd+2 ...)
first byte -- header. image width (in tiles)

next bytes -- runs. type of run described by the two least significant bits of the first byte of each run
according to the folowing:

%nnnnnn01 -- dd : run of n+2 (2 to 65) *same word* value HHdd (a.k.a. "normal" RLE)
%nnnnnn11 -- dd : run of n+2 (2 to 65) *successive word* values (HHdd, HHdd+1, HHdd+2 ...)
: will eventually change HH too!
%nnnnnn00 -- dd kk pp [...] : run of n (1 to 63) words using each of the following bytes (HHdd, HHkk, HHpp...)
: n=0 means end of compressed data
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