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**
** $Id: $
** $Revision: $
**
** $Filename: GetViewModes.S $
** $Author: Christian A. Weber $
** $Release: 19.1 $
** $Date: 92/05/11 21:11:27 $
**
** iff.library/IFFLib_GetViewModes
**
** 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 IFFLib_GetViewModes
SECTION text,CODE
INCLUDE "IffLib.i"
XREF FindChunkFunc,GetBMHDFunc
XDEF CalcViewModes ; für SaveClip.S
XDEF GetViewModesFunc
******* iff.library/IFFLib_GetViewModes **************************************
*
* NAME
* IFFLib_GetViewModes() -- Get Amiga-specific ViewModes
*
* SYNOPSIS
* viewmodes = IFFLib_GetViewModes( ifffile )
* D0 A1
*
* ULONG IFFLib_GetViewModes( IFFFILE )
*
* FUNCTION
* Searches the IFF file for a 'CAMG' chunk which holds the view modes
* information. If there is no CAMG chunk, the view modes are calcu-
* lated using the information in the BitMapHeader structure.
* You can directly put the low WORD of the result of a GetViewModes()
* call into the ns_ViewModes field of a NewScreen structure. All
* forbidden bits are masked out, as suggested by CBM.
*
* INPUTS
* ifffile - IFF file pointer, returned from OpenIFF()
*
* RESULT
* viewmodes - LONG containing the view modes (HAM, LACE, HIRES ...)
* Under Kickstart V1.3, only the lower WORD is used.
*
* BUGS
* If the IFF file has no CAMG chunk and 6 bitplanes, the HAM bit
* will be set. This is not always correct since the picture could
* be in the Extra Halfbrite mode. You can load such Halfbrite
* pictures into DPaint III and save them again, DPaint will generate
* the correct CAMG chunk.
*
* SEE ALSO
*
*****************************************************************************
*** Flags, die nur in graphics/view.h aber nicht .i sind (!)
HAM: EQU $0800
SPRITES: EQU $4000
VP_HIDE: EQU $2000
GENLOCK_AUDIO: EQU $0100
GENLOCK_VIDEO: EQU $0002
EXTRA_HALFBRITE: EQU $0080
MODESMASK: EQU ~(SPRITES|VP_HIDE|GENLOCK_AUDIO|GENLOCK_VIDEO)
GetViewModesFunc:
move.l a2,-(SP)
movea.l a1,a2 ; A2 : IFFFile
move.l #'CAMG',d0
bsr FindChunkFunc ; setzt Z-Flag wenn not found
beq.s CalcEm ; not found ---> Berechnen
movea.l d0,a0 ; Zeiger auf CAMG....
move.l 8(a0),d0 ; ViewModes
andi.l #MODESMASK,d0 ; Verbotene Bits ausmaskieren
bra.s Ende ; --->
*** ViewModes aus BMHD berechnen, 0 falls kein CAMG
CalcEm: movea.l a2,a1 ; IFFFile
bsr GetBMHDFunc ; BitMapHeader suchen
;; tst.l d0 ; nicht gefunden?
beq.s Ende ; dann 0 zurückgeben
movea.l d0,a0 ; A0 : BMHD-Struktur
bsr.s CalcViewModes ; ViewModes nach D0
cmpi.b #6,bmh_nPlanes(a0) ; 6 Bitplanes ?
blt.s Ende ; nein --->
bset #11,d0 ; ViewModes |= HAM
Ende:
movea.l (SP)+,a2
rts
*** ViewModes berechnen, A0 = struct BitMapHeader
*** Diese Routine wird auch von SaveClip() benutzt
CalcViewModes: moveq.l #0,d0 ; D0 : ViewModes
cmpi.b #4,bmh_nPlanes(a0) ; mehr als 4 Planes ?
bgt.s NotHiRes ; ja ---> nicht HiRes
cmpi.w #400,bmh_Width(a0) ; Bildbreite > 400 ?
ble.s NotHiRes ; nein --->
bset #15,d0 ; ViewModes |= HiRes
NotHiRes:
cmpi.w #320,bmh_Height(a0) ; Bildhöhe > 320 ?
blt.s NotInterlace ; nein --->
bset #2,d0 ; ViewModes |= Interlace
NotInterlace:
rts
END
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