World of A1200/World_Of_A1200.iso/programs/graphics/fractals/mandelbrute 1.2/src.lha/src/MandelBrute.c

C/C++ Source or Header | 1993-09-24 | 4KB | 208 lines

/*
Copyright (C) 1993 George Leonidas Coulouris

Program    name    : MandelBrute
Description    : Computes an image of (z**2 + c) in the complex plane
Last modified    : 24 Sep 93

To do:
    Fix color scaling bug
*/

/* - Preprocessor ------------------------------------------------ */

/*
    USE881 is only set for Amiga users with SAS/C and MC68881s
    COLSPERCOMP <= 256
    NUMCOLS = COLSPERCOMP ** 3
*/

#define USE881

#define NUMCOLS        16777216    /* total number of colors */
#define COLSPERCOMP    256        /* colors per component */

#include <stdio.h>
#include <stdlib.h>

#ifdef USE881
#include <m68881.h>
#else
#include <math.h>
#endif

/* - Declarations ------------------------------------------------ */

unsigned short iterations;    /* maximum iterations */

double IterateC(double cx,double cy);

/* - Main -------------------------------------------------------- */

void main(int argc,char *argv[])
{

register unsigned short
    x,                /* pixel index */
    y,                /* raster index */
    width,                /* pixelmap width */
    height;                /* pixelmap height */

register unsigned long
    tmpr;                /* temporary radius */

unsigned char
    tmp;                /* temporary counter */

double
    corners[4],            /* radii of corners */
    maxr,                /* maximum radius */
    scalefactor,            /* color scale factor */
    xmin,                /* real minimum */
    xmax,                /* real maximum */
    xfrac,                /* real increment */
    ymin,                /* imaginary minimum */
    ymax,                /* imaginary maximum */
    yfrac;                /* imaginary increment */

FILE *fp;

                    /* banner */
printf("MandelBrute 1.2 (24 Sep 93)\n");
printf("Copyright (C) 1993 George Leonidas Coulouris\n\n");

                    /* check argument list */
if (argc != 9)
    {
    printf("usage: MandelBrute <file> <xmin> <xmax> <ymin> <ymax> <iterations> <width> <height>\n\n");
    exit(0);
    }

                    /* check & open file */
if ((fp = fopen(argv[1],"w+")) == NULL)
    {
    printf("File could not be opened.\n\n");
    exit(1);
    }

                    /* parse arguments */
xmin        = atof(argv[2]);
xmax        = atof(argv[3]);
ymin        = atof(argv[4]);
ymax        = atof(argv[5]);
iterations    = atoi(argv[6]);
width        = atoi(argv[7]);
height        = atoi(argv[8]);

                    /* check arguments */
if ((xmin >= xmax) || (ymin >= ymax) )
    {
    printf("Bad coordinates.\n\n");
    exit(1);
    }

if (iterations <= 0)
    {
    printf("Bad iterations.\n\n");
    exit(1);
    }

if ( (width <= 0) || (height <= 0) )
    {
    printf("Bad image dimensions.\n\n");
    exit(1);
    }

                    /* compute corner radii */
corners[0] = IterateC(xmin,ymin);
corners[1] = IterateC(xmin,ymax);
corners[2] = IterateC(xmax,ymin);
corners[3] = IterateC(xmax,ymax);

                    /* find maximum radius */
for(tmp=0;tmp<3;tmp++)
    maxr = (corners[tmp] > corners[tmp+1]) ? corners[tmp] : corners[tmp+1];

                    /* compute increments */
xfrac         = fabs((xmax-xmin)) / width;
yfrac         = fabs((ymax-ymin)) / height;

                    /* compute color scale factor */
scalefactor    = (NUMCOLS-1) / maxr;

/*
    The following four statements write the PPM header.
*/

fprintf(fp,"P6\n");
fprintf(fp,"%d\n",width);
fprintf(fp,"%d\n",height);
fprintf(fp,"%d\n",(COLSPERCOMP-1));

for(y=0;y<height;y++)        /* number crunching loops */
    {
    printf("Line %5d\r",y);
    for(x=0;x<width;x++)
        {
        tmpr = (long)(scalefactor * IterateC( (xmin + x*xfrac) , (ymin + (height-y)*yfrac) ) );

/*
    The following three statements extract the red, green, and blue
components of the pixel, and write them to the ppm file.
*/

        fputc( (int)((COLSPERCOMP-1) * tmpr / (NUMCOLS-1)) ,fp);

        fputc( (int)((tmpr/COLSPERCOMP) % COLSPERCOMP), fp);

        fputc( (int)(tmpr % COLSPERCOMP) ,fp);
        }
    }

                    /* Close up and exit */
if (fclose(fp) == EOF)
    {
    printf("File could not be closed.\n");
    exit(1);
    }
else
    {
    printf("Operation complete.\n");
    exit(0);
    }

}

/* - Functions --------------------------------------------------- */

double IterateC(double cx,double cy)
/*
Arguments    : cx, cy
Value        : 0 if c in Mandelbrot set, else escape radius
*/
{
unsigned short i;            /* Iteration index */

double
    oldzx = 0,            /* Initial z seeds */
    oldzy = 0,
    zx,
    zy,
    r;

for(i=0;i<iterations;i++)
    {
    zx = oldzx * oldzx - oldzy * oldzy + cx;
    zy = 2.0 * oldzx * oldzy + cy;
    r = zx * zx + zy * zy;

    if (r > 4.0) return sqrt(r);
    else
        {
        oldzx = zx;
        oldzy = zy;
        }
    }
return 0;
}