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**
** $Id: GetColorTab.S,v 21.1 92/05/15 03:22:16 chris Exp $
** $Revision: 21.1 $
**
** $Filename: GetColorTab.S $
** $Author: chris $
** $Date: 92/05/15 03:22:16 $
**
** iff.library/IFFL_GetColorTab
**
** 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_GetColorTab
SECTION text,CODE
INCLUDE "IFFLib.i"
XREF FindChunkFunc
XDEF GetColorTabFunc
******* iff.library/IFFL_GetColorTab ****************************************
*
* NAME
* IFFL_GetColorTab -- find a CMAP and convert it to a ColorTable
*
* SYNOPSIS
* count = IFFL_GetColorTab( iff, colortable )
* D0 A1 A0
*
* LONG IFFFL_GetColorTab( IFF_HANDLE, UWORD * )
*
* FUNCTION
* Searches the CMAP chunk of an IFF file and converts it, if it's
* there, to an Amiga color table structure. This colortable can
* directly be used as a parameter for the LoadRGB4() function.
*
* INPUTS
* iff - IFF file handle, from IFFL_OpenIFF()
* colortable - Pointer to a block of memory which must be large
* enough to hold the colortable (2 bytes per color).
* Must be WORD aligned.
*
* RESULT
* Number of colors actually found, or zero if the file has no
* CMAP chunk
*
* SEE ALSO
* IFFL_FindChunk(), IFFL_GetBMHD()
*
*****************************************************************************
GetColorTabFunc:
movem.l d2-d5/a2,-(SP)
movea.l a0,a2 ; Ziel-Adresse
move.l #'CMAP',d0
bsr FindChunkFunc
;; tst.l d0
beq.s 99$ ; nicht gefunden --->
movea.l d0,a0
addq.l #4,a0 ; Chunk-Namen überlesen
move.l (a0)+,d4 ; Chunk-size
divs #3,d4 ; Anzahl Farben
ext.l d4 ; für D0
move.l d4,d0 ; Resultat: Anzahl Farben
moveq #256-$f0,d5 ; Color-Maske $f0
neg.b d5 ; Toebes-Optimierlung
bra.s 1$ ; Für dbf
.Loop: move.b (a0)+,d1 ; rot
and.w d5,d1 ; Nur Bits 7-4 benützen
move.b (a0)+,d2 ; grün
and.w d5,d2 ; Nur Bits 7-4 benützen
move.b (a0)+,d3 ; blau
and.w d5,d3 ; Nur Bits 7-4 benützen
lsl.w #4,d1 ; rot << 4
lsr.w #4,d3 ; blau >> 4
or.w d2,d1
or.w d3,d1
move.w d1,(a2)+ ; in Farbtabelle eintragen
1$: dbf d4,.Loop
99$:
movem.l (SP)+,d2-d5/a2
rts
END
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