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**
** $Id: DecodePic.S,v 21.2 92/05/18 02:16:02 chris Exp $
** $Revision: 21.2 $
**
** $Filename: DecodePic.S $
** $Author: chris $
** $Release: 19.1 $
** $Date: 92/05/18 02:16:02 $
**
** iff.library/IFFL_DecodePic
**
** COPYRIGHT (C) 1987-1992 BY CHRISTIAN A. WEBER, BRUGGERWEG 2,
** CH-8037 ZUERICH, SWITZERLAND. ALL RIGHTS RESERVED. NO PART
** OF THIS SOFTWARE MAY BE COPIED, REPRODUCED, OR TRANSMITTED
** IN ANY FORM OR BY ANY MEANS, WITHOUT THE PRIOR WRITTEN PER-
** MISSION OF THE AUTHOR. USE AT YOUR OWN RISK.
**
IDNT IFFL_DecodePic
SECTION text,CODE
INCLUDE "IFFLib.i"
XREF ClearError,SetError,Decompress_BYTERUN1
XREF GetBMHDFunc,FindChunkFunc
XDEF DecodePicFunc
******* iff.library/IFFL_DecodePic ******************************************
*
* NAME
* IFFL_DecodePic -- decode the BODY of an ILBM file into a BitMap
*
* SYNOPSIS
* success = IFFL_DecodePic( iff, bitmap )
* D0 A1 A0
*
* BOOL IFFL_DecodePic( IFFL_HANDLE, struct BitMap * )
*
* FUNCTION
* Decodes and decompresses a picture into the user supplied BitMap.
* If the picture is higher than your BitMap, it will be truncated.
* If your BitMap is larger than the picture, the picture will be
* drawn into the top left corner of your BitMap.
* If the picture has less planes than the BitMap, the unused planes
* are NOT touched by this routine, so you may wish to clear them
* before calling IFFL_DecodePic(). If the picture has more planes
* than your BitMap, the surplus planes of the picture are ignored.
*
* INPUTS
* iff - IFF file handle, from IFFL_OpenIFF()
* bitmap - Pointer to a properly initialized BitMap structure:
* bm_Planes[] must point to valid BitPlanes,
* bm_Depth contains the number of planes.
* bm_Width and bm_Height must be set according to the
* size of your bit planes.
*
* RESULTS
* Non-zero if successful, zero if error. Call IFFL_IFFError() to
* know the reason of the failure
*
* BUGS
* If the picture is wider than your BitMap, one line of innocent
* memory will be overwritten at the end of each bitplane. You can
* avoid this by allocating a few bytes more for each plane.
* Normally, you allocate your BitMap after inspecting the BMHD
* chunk, so this should not be a problem.
*
* NOTE
* This routine needs at least 650 bytes of stack space
*
* SEE ALSO
*
*****************************************************************************
STRUCTURE DecodePicStackFrame,0
STRUCT WorkPlanes,24*4 ; muß am Anfang sein
STRUCT LineBuffer,400 ; max 3200 pixel bei stencil
LABEL LINKSIZE
DecodePicFunc: movem.l d2-d7/a2-a6,-(SP)
lea -LINKSIZE(SP),SP ; Lokalen Datenraum schaffen
movea.l a6,a5 ; A5: IFFBase für SetError()
movea.l a0,a3 ; A3: BitMap
movea.l a1,a4 ; A4: IFFFile
*** Testen ob ILBM-File
cmpi.l #'ILBM',8(a4) ; ist's überhaupt ein ILBM-File ?
beq.b 1$ ; ja --->
moveq #IFFL_ERROR_NOILBM,d0 ; Fehlernummer
bra .Error
1$:
*** BitMapHeader suchen und nach A2
bsr GetBMHDFunc ; BitMapHeader suchen
;; tst.l d0
bne.b 2$ ; gefunden --->
moveq #IFFL_ERROR_NOBMHD,d0 ; Fehlernummer
bra .Error
2$: movea.l d0,a2 ; A2: BitMapHeader
*** Testen ob Bild-Depth <= BitMap Depth
move.b bmh_nPlanes(a2),d2 ; D2: Depth (Minimum)
beq .Okay ; Bild hat 0 planes --->
3$:
*** Planes in Arbeitsbereich kopieren
moveq.l #23,d0 ; Max. 24 Bitplanes
lea bm_Planes(a3),a0 ; Source
lea WorkPlanes(SP),a1 ; Destination
.CopyLoop: move.l (a0)+,(a1)+
dbf d0,.CopyLoop
*** BODY-Chunk suchen und nach A0, BODY-Ende nach A4
move.l #'BODY',d0
movea.l a4,a1 ; IFF-File
bsr FindChunkFunc
;; tst.l d0
bne.b 4$ ; gefunden --->
moveq #IFFL_ERROR_NOBODY,d0 ; Fehlernummer
bra .Error
4$:
movea.l d0,a0 ; A0 : Body-Adresse
addq.l #4,a0 ; 'BODY' überspringen
movea.l (a0)+,a4 ; Chunk-size
adda.l a0,a4 ; A4 : Body-Endadresse
*** Compression testen und entsprechende Routine nach A6
move.b bmh_Compression(a2),d0
bne.b 5$
lea CopyRow(PC),a6 ; Not crunched
bra.b 7$ ; --->
5$:
subq.b #1,d0 ; CmpByteRun1 ?
bne.b 6$ ; ja --->
lea Decompress_BYTERUN1(PC),a6 ; DecompressBlock.S
bra.b 7$ ; --->
6$:
moveq #IFFL_ERROR_BADCOMPRESSION,d0
bra.b .Error
7$:
*** Masking testen und wenn 'hasmask' (Stencil) D7.B:=$FF, sonst $00
cmpi.b #1,bmh_Masking(a2) ; 'mskHasMask' ?
seq d7 ; wenn ja: D7 := $FF
*** Modulos setzen etc.
.doit: moveq.l #0,d4 ; D4 : Source-Modulo
move.w bmh_Width(a2),d4
add.w #15,d4 ; auf WORD aufrunden
lsr.l #3,d4
bclr #0,d4 ; auf WORD aufrunden
moveq.l #0,d5
move.w bm_BytesPerRow(a3),d5 ; D5 : Destination-Modulo
moveq.l #0,d6
move.w bm_Rows(a3),d6 ; D6 : Max. Anzahl Zeilen
cmp.w bmh_Height(a2),d6 ; BitMap zu groß ?
ble.b 8$ ; nein --->
move.w bmh_Height(a2),d6 ; Sonst Höhe aus bmh nehmen
8$:
bra.b .CheckCond ; ---> für dbf
*** Hauptschleife
.body1: moveq #0,d3 ; Init plane-counter
lea WorkPlanes(SP),a2 ; A2 : Arbeitskopie der Planes
.body2: move.l d4,d0 ; Source bytes per row
cmp.b bm_Depth(a3),d3 ; Is there a dest-plane ?
bhs.b .NoDest ; nope ---> skip it
movea.l (a2),a1 ; Adrese der aktuellen Plane
add.l d5,(a2)+ ; Plane auf nächste Linie
bra.b 9$
.NoDest: lea LineBuffer(SP),a1 ; Plane ins NIL kopieren
9$: jsr (a6) ; Linie copyren / decrunchen
addq.b #1,d3 ; INC planecounter
cmp.b d2,d3
blt.b .body2 ; ---> Nächste Plane
tst.b d7 ; Maske zu überhüpfen ?
beq.b .NoMask ; nein --->
move.l d4,d0 ; Source bytes per row
lea LineBuffer(SP),a1 ; Maske zur Hölle schicken
jsr (a6) ; Linie copyren / decrunchen
.NoMask:
.CheckCond: cmpa.l a4,a0 ; fertig ?
dbhs d6,.body1 ; wenn nicht: nächste Linie
.Okay: bsr ClearError ; IFFError rücksetzen, D0 := 1
bra.b .Ende
.Error: bsr SetError ; IFFError setzen, clr.l d0
.Ende: lea LINKSIZE(SP),SP
movem.l (SP)+,d2-d7/a2-a6
rts
*************** 1 Linie kopieren *****************************************
copyloop: move.b (a0)+,(a1)+
CopyRow: dbf d0,copyloop
rts
END
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