Path: csus.edu!wuarchive!julius.cs.uiuc.edu!news.cs.indiana.edu!iuvax!copper!blank
From: blank@copper.ucs.indiana.edu (doug blank)
Newsgroups: alt.fractals.pictures
Subject: Fractal Pictures
Message-ID: <76832@iuvax.cs.indiana.edu>
Date: 6 Dec 90 18:00:20 GMT
References: <28420@usc>
Sender: news@iuvax.cs.indiana.edu
Distribution: ca
Organization: Indiana University, Bloomington IN.
Lines: 192

We just picked up this newsgroup here at Indiana U, and its
interesting to see so many exploring the world of fractals. I was a
bit (maybe even a byte) confusued though to see that these were the
actual postings of the pictures. Wouldn't it save much time and space
to just send the coordinates or magnification of the beautiful spots
and let each generate? Maybe some would take awhile on a pc, but at
a 1200 baud download, which is faster?

Here are two files which allow the generation and display of spots in
the Mandelbrot set. They are divided into two programs so that you
could generate them on the fastest computer you have access to, and
then display them on a pc. The display program is set up for four
colors at present. The gif, gem, etc, formats are probably much more
complicated, but if you could list the coordinates or magnification
when you find a spectaular place in the Mandelbrot set, some of us
could generate it. Maybe others have written code that generates other
formats (gem, gif) and would be willing to share.

-doug blank
blank@iuvax.cs.indiana.edu

p.s. - I have heard rumours that the phrase "Paul is dead" can be found
somewhere in the Mandelbrot set. 

-----------------------------------------------

/*                   File generate.c                   */

/* By Jim Marshall and Doug Blank                      */

/* B-row by A-column pixel matrix is stored as a linear file of ASCII
   characters in top-down row-major order.  Thus, the first A characters
   correspond to the top row of the screen, the next A characters
   correspond to the row 2nd from the top, and so on.  Each matrix entry
   stores the number of iterations required for the entry's associated
   complex number to escape to infinity, or zero if the number falls within
   the Mandelbrot Set.  A number N is stored in the file as an ASCII char-
   acter of code N. */

#include <stdio.h>

char mode;
char filename[15];
int A,B,MAXK,np,nq,k;
double p,q,pmin,pmax,qmin,qmax,deltap,deltaq,pside,qside,padjust,qadjust;
double M,METRIC,R,r,ratio,mag,x,y,xnext,ynext;
FILE *fopen(),*fp;
 
main()
{
   A = 320;       /* horizontal screen resolution (pixels) */
   B = 200;       /* vertical screen resolution (pixels) */
   R = 0.7;       /* ratio of screen height to screen width */
   METRIC = 3.0;  /* imaginary range size at magnification = 1.0 */
   MAXK = 200;    /* maximum number of iterations to perform at each point */
   M = 100.0;
 
   printf("\nSpecify window using coordinates or magnification? (c/m): ");
   scanf("%c",&mode);

   if (mode == 'm') {

      printf("Enter central coordinate (real, imaginary): ");
      scanf("%f %f",&p,&q);
      printf("Enter magnification factor: ");
      scanf("%f",&mag);

      qadjust = METRIC/(2.0*mag);
      padjust = qadjust/R;
      pmin = p - padjust;
      pmax = p + padjust;
      qmin = q - qadjust;
      qmax = q + qadjust;

   } else {

      printf("Enter real minimum, maximum values: ");
      scanf("%f %f",&pmin,&pmax);
      printf("Enter imaginary minimum, maximum values: ");
      scanf("%f %f",&qmin,&qmax);

      pside = pmax - pmin;
      qside = qmax - qmin;
      ratio = qside/pside;
      if (ratio < R) {
         qadjust = (R*pside - qside)/2.0;
         qmin = qmin - qadjust;
         qmax = qmax + qadjust; }
      if (ratio > R) {
         padjust = (qside/R - pside)/2.0;
         pmin = pmin - padjust;
         pmax = pmax + padjust; }

    }

   printf("Real range scaled to:      %g to %g\n",pmin,pmax);
   printf("Imaginary range scaled to: %g to %g\n",qmin,qmax);
   printf("Enter name of output file: ");
   scanf("%s",filename);

   deltap = (pmax - pmin)/(A - 1);
   deltaq = (qmax - qmin)/(B - 1);

   fp = fopen(filename,"w");

   for (nq = 0; nq < B; ++nq) {
      for (np = 0; np < A; ++np) {

	 p = pmin + (np * deltap);
	 q = qmax - (nq * deltaq);
	 x = 0.0;
	 y = 0.0;
	 k = 0;

	 do {  /* iterate critical point (x,y) = (0,0) with parameter (p,q) */
	    xnext = x*x - y*y + p;
	    ynext = 2.0*x*y + q;
	    x = xnext;
	    y = ynext;
	    ++k;
	    r = x*x + y*y;
	 } while ((r <= M) && (k < MAXK));
 
      if (r > M)
	 putc(k+32,fp);
      else
         putc(0,fp);
      }
   }
   fclose(fp);
}
/* EOF of fract.c                              */

---------------------------------------------------------

/*                        File display.c       */
/* Written by Jim Marshall and Doug Blank      */

#include <graph.h>
#include <stdio.h>
#include <dos.h>

int     A,
        B,
        np,
        nq,
        k,
        color;
void keyboard (void);
main () {
    A = 640;			/* horizontal screen resolution (pixels) 
				*/
    B = 350;			/* vertical screen resolution (pixels) */

    _setvideomode (_ERESCOLOR);

    for (nq = 0; nq < B; ++nq) {
	for (np = 0; np < A; ++np) {
	    scanf ("%c", &k);
	    if (k == 32)
		color = 0;
	    else
		color = ((k - 32) % 4) + 1;
	    _setcolor (color);
	    _setpixel (np, nq);
	}
    }
    keyboard ();
    _clearscreen (_GCLEARSCREEN);
    _setvideomode (_DEFAULTMODE);
    exit (0);
}

void keyboard (void) {
    union u_type {
	int     a;
	char    b[3];
    } keystroke;
    int     get_keystroke (void);
    do
	keystroke.a = get_keystroke ();
    while (keystroke.b[0] != 27);
}
int     get_keystroke (void) {
            union REGS regs;
    regs.h.ah = 0;
    return int86 (0x16, &regs, &regs);
}
=====================================================================
blank@iuvax.cs.indiana.edu          Douglas Blank, Indiana University
---------------------------------------------------------------------
Computer Science                                    Cognitive Science