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**
** $Id: GetViewModes.S,v 21.2 92/05/18 02:18:15 chris Exp $
** $Revision: 21.2 $
**
** $Filename: GetViewModes.S $
** $Author: chris $
** $Date: 92/05/18 02:18:15 $
**
** iff.library/IFFL_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 IFFL_GetViewModes
SECTION text,CODE
INCLUDE "graphics/view.i"
INCLUDE "IffLib.i"
XREF FindChunkFunc,GetBMHDFunc
XDEF CalcViewModes ; für SaveClip.S
XDEF GetViewModesFunc
******* iff.library/IFFL_GetViewModes ***************************************
*
* NAME
* IFFL_GetViewModes() -- Get Amiga-specific ViewModes
*
* SYNOPSIS
* viewmodes = IFFL_GetViewModes( iff )
* D0 A1
*
* ULONG IFFL_GetViewModes( IFFL_HANDLE )
*
* 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 call to
* IFFL_ GetViewModes() into the ns_ViewModes field of a NewScreen
* structure, or you can use the whole ULONG for the SA_DisplayID tag
* under OS 2.x.
*
* INPUTS
* iff - IFF file handle, from OpenIFF()
*
* RESULT
* viewmodes - ULONG containing the view modes (HAM, LACE, HIRES ...)
* All forbidden bits are masked out, as suggested by CBM.
* 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
* <graphics/displayinfo.h>
*
*****************************************************************************
MODESMASK EQU ~(V_SPRITES|V_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.b CalcEm ; not found ---> Berechnen
movea.l d0,a0 ; Zeiger auf CAMG....
move.l 8(a0),d0 ; ViewModes
tst.w 8(a0) ; Oberes WORD == 0 ?
bne.b 1$ ; Nein ---> Nix ausmaskieren
andi.l #MODESMASK,d0 ; Verbotene Bits ausmaskieren
1$: bra.b Ende ; --->
*** ViewModes aus BMHD berechnen, 0 falls kein BMHD
CalcEm: movea.l a2,a1 ; IFFFile
bsr GetBMHDFunc ; BitMapHeader suchen
;; tst.l d0 ; nicht gefunden?
beq.b Ende ; dann 0 zurückgeben
movea.l d0,a0 ; A0 : BMHD-Struktur
bsr.b CalcViewModes ; ViewModes nach D0
IFD OLDBADHAMPICTURES
cmpi.b #6,bmh_nPlanes(a0) ; 6 Bitplanes ?
blt.b Ende ; nein --->
bset #11,d0 ; ViewModes |= HAM
ENDC
Ende:
movea.l (SP)+,a2
rts
*****i* iff.library/CalcViewModes *******************************************
*
* NAME
* CalcViewModes() -- Calculate Amiga-specific ViewModes from a BMHD
*
* SYNOPSIS
* viewmodes = CalcViewModes( bmhd )
* D0 A0
*
* ULONG CalcViewModes( struct IFFL_BMHD )
*
* FUNCTION
* Tries to calculate the viewmodes for a CAMG chunk by looking at
* the bmh_Width, bmh_Height and bmh_Depth entries of a bmhd.
* This is not always satisfactory, but we're stuck with it.
*
* INPUTS
* bmhd - BitMapHeader describing the picture's dimensions
*
* RESULT
* viewmodes - ULONG containing the view modes (LACE, HIRES)
*
* BUGS
* Knows nothing about Monitor IDs or new View modes like SUPERHIRES
* or HAM8. You should not use this function in new code.
*
* SEE ALSO
* IFFL_GetViewModes(), IFFL_SaveClip()
*
*****************************************************************************
CalcViewModes: moveq.l #0,d0 ; D0 : ViewModes
cmpi.b #4,bmh_nPlanes(a0) ; mehr als 4 Planes ?
bgt.b NotHiRes ; ja ---> nicht HiRes
cmpi.w #400,bmh_Width(a0) ; Bildbreite > 400 ?
ble.b NotHiRes ; nein --->
bset #15,d0 ; ViewModes |= HiRes
NotHiRes:
cmpi.w #320,bmh_Height(a0) ; Bildhöhe > 320 ?
blt.b NotInterlace ; nein --->
bset #2,d0 ; ViewModes |= Interlace
NotInterlace:
rts
END
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