From 36c824864c02f0a3f62c8a1d365d1670835c8c96 Mon Sep 17 00:00:00 2001
From: "Christian A. Weber" <chris@gna.ch>
Date: Tue, 12 May 1992 22:26:12 +0000
Subject: Initial revision

---
 Source/GetViewModes.S | 124 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 124 insertions(+)
 create mode 100644 Source/GetViewModes.S

(limited to 'Source/GetViewModes.S')

diff --git a/Source/GetViewModes.S b/Source/GetViewModes.S
new file mode 100644
index 0000000..e6a10c6
--- /dev/null
+++ b/Source/GetViewModes.S
@@ -0,0 +1,124 @@
+**
+**	$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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