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From: lsmichae@immd4.informatik.uni-erlangen.de (Lars Michael)
Newsgroups: comp.sys.atari.st
Subject: Re: Reading a Lores Screen
Message-ID: <1991Mar6.184558.29034@informatik.uni-erlangen.de>
Date: 6 Mar 91 18:45:58 GMT
References: <9103052219.aa11315@Bonnie.ics.uci.edu>
Organization: CSD., University of Erlangen, Germany
Lines: 31

bferrer@Bonnie.ICS.UCI.EDU writes:


>  Given a pointer to a lores screen, how can I read a pallete number
>from the screen without using the linea routines but with pointer
>manipulation?

A C-routine to get the color index of point (x, y):

int get_pix(int x, int y, char *Screen)
{	int Index;
	int mapnr;

	Screen += 160*y + ((x & 0xfff0) >> 1) + (x>7?:0:1);
        bitnr = 7 - x % 8;
	for (Index=0, mapnr=0; mapnr<4; mapnr+=1, Screen+=2)
		Index |= ((*Screen >> bitnr) & 1) << mapnr;
	return (Index);
}

Have fun !!!


								Lars

+-----------------------------------+----------------------------------+
|  Lars Michael                     |    | | |                         |
|  lsmichae@faui43.uni-erlangen.de  |    | | |   "Down with ATARI,     |
+-----------------------------------+   /  |  \   Long live the ST !"  |
|  "May the Schwartz be with you!"  |  /   |   \                       |
+-----------------------------------+----------------------------------+