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Amiga ACS 1998 #6
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amigaacscoverdisc1998-061998.iso
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descent
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2d
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effects.c
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1998-06-08
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/*
THE COMPUTER CODE CONTAINED HEREIN IS THE SOLE PROPERTY OF PARALLAX
SOFTWARE CORPORATION ("PARALLAX"). PARALLAX, IN DISTRIBUTING THE CODE TO
END-USERS, AND SUBJECT TO ALL OF THE TERMS AND CONDITIONS HEREIN, GRANTS A
ROYALTY-FREE, PERPETUAL LICENSE TO SUCH END-USERS FOR USE BY SUCH END-USERS
IN USING, DISPLAYING, AND CREATING DERIVATIVE WORKS THEREOF, SO LONG AS
SUCH USE, DISPLAY OR CREATION IS FOR NON-COMMERCIAL, ROYALTY OR REVENUE
FREE PURPOSES. IN NO EVENT SHALL THE END-USER USE THE COMPUTER CODE
CONTAINED HEREIN FOR REVENUE-BEARING PURPOSES. THE END-USER UNDERSTANDS
AND AGREES TO THE TERMS HEREIN AND ACCEPTS THE SAME BY USE OF THIS FILE.
COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION. ALL RIGHTS RESERVED.
*/
/*
* $Source: f:/miner/source/2d/rcs/effects.c $
* $Revision: 1.5 $
* $Author: john $
* $Date: 1994/11/18 22:51:04 $
*
* special effects stuff
*
* $Log: effects.c $
* Revision 1.5 1994/11/18 22:51:04 john
* Changed a bunch of shorts to ints in calls.
*
* Revision 1.4 1994/04/22 11:16:00 john
* *** empty log message ***
*
* Revision 1.3 1994/02/01 13:18:45 john
* *** empty log message ***
*
* Revision 1.2 1993/10/26 13:18:15 john
* *** empty log message ***
*
* Revision 1.1 1993/10/25 14:56:56 john
* Initial revision
*
*
*/
#pragma off (unreferenced)
static char rcsid[] = "$Id: effects.c 1.5 1994/11/18 22:51:04 john Exp $";
#pragma on (unreferenced)
#include <stdlib.h>
#include <stdio.h>
#include "mem.h"
#include "gr.h"
#include "grdef.h"
#include "effect2d.h"
int bitwidth(unsigned int n)
{
int width = 0;
while ( n!=0 ) {
n >>= 1;
width++;
}
return width;
}
long randmasks[] = { 0,0,0x03,0x06,0x0c,0x14,0x30,0x60,0xb8,\
0x110,0x240,0x500,0xca0,0x1b00,0x3500,0x6000,0xb400,\
0x12000,0x204000,0x720000,0x90000,0x140000,0x300000,0x400000,\
0xd80000,0x1200000,0x3880000,0x7200000,0x9000000,0x14000000,\
0x32800000,0x48000000,0xa3000000 };
void dissolve_in(grs_bitmap * bitmap )
{
int height, width, zz;
int rwidth, cwidth; /* bit width for rows, for columns */
int regwidth; /* "width" of sequence generator */
long mask; /* mask to XOR with to create sequence */
int rowshift; /* shift distance to get row */
/* from element */
int colmask; /* mask to extract column from element */
unsigned long element; /* one element of random */ /* sequence */
int row, column; /* row and column for one pixel */
/* Find the mask to produce all rows and columns. */
height = bitmap->bm_h;
width = bitmap->bm_w;
rwidth = bitwidth (height); /* how many bits needed for height? */
cwidth = bitwidth (width); /* how many bits needed for width? */
regwidth = rwidth + cwidth; /* how wide must the register be? */
mask = randmasks[regwidth]; /* which mask is for that width? */
/* Find values to extract row and col numbers from each element. */
rowshift = cwidth; /* find dist to shift to get top bits (row) */
colmask = (1<<cwidth)-1; /* find mask to extract */
/* bottom bits (col) */
/* Now cycle through all sequence elements. */
element = 1; /* 1st element (could be any nonzero) */
do {
for (zz=0; zz < 100; zz++);
row = element >> rowshift; /* find row number for this pixel */
column = element & colmask; /* and how many columns across? */
/* does element fall in the array? */
/* ...must check row AND column */
if ((row < height) && (column < width)) {
// Draw the (r,c)'th pixel
gr_setcolor(gr_ugpixel( bitmap, column, row ));
gr_upixel(column, row);
}
/* Compute the next sequence element */
if (element & 1) /* is the low bit set? */
element = (element >>1)^mask; /* yes: shift value, */
else
element = (element >>1); /* no: just shift the value */
} while (element != 1); /* loop until we return to */
/* original element */
gr_setcolor(gr_ugpixel( bitmap, 0, 0 ));
gr_upixel(0,0);
}