juliamath.c - fracwall - This fractal wallpaper generator creates a bitmap file depicting either the Mandelbrot or the Julia set

juliamath.c (2518B)
      1 /*
      2   Back-end Math for the Julia/Mandelbrot Set implementation file
      3   "juliamath.c"
      4   M. Yamanaka
      5   email: myamanaka@live.com
      6   website: csmyamanaka.com
      7   license: MIT (See included "LICENSE" file for details)
      8 */
      9 
     10 #include "juliamath.h"
     11 
     12 int cmplxAdd(float* rz, float* op1, float* op2){
     13   /*
     14     op1 ... first operand
     15     op2 ... second operand
     16     rz  ... result
     17   */
     18   rz[0] = op1[0] + op2[0];
     19   rz[1] = op1[1] + op2[1];
     20   return 0;
     21 }
     22 
     23 int cmplxMult(float* rz, float* op1, float* op2){
     24   /*
     25     op1 ... first operand
     26     op2 ... second operand
     27     rz  ... result
     28   */
     29   rz[0] = op1[0]*op2[0] - op1[1]*op2[1];
     30   rz[1] = op1[0]*op2[1] + op1[1]*op2[0];
     31   return 0;
     32 }
     33 
     34 float cmplxLenSq(float* ipt){
     35   /*
     36     ipt ... input complex number
     37   */
     38   return ipt[0]*ipt[0] + ipt[1]*ipt[1];
     39 }
     40 
     41 float convNtoR(int ipt, int sz, float cmin, float cmax){
     42   /*
     43     ipt   ... number pending conversion
     44     sz    ... image length in a given dimension before conversion
     45     cmin  ... mininum value of a given axis on the complex plane
     46     cmax  ... maximun " " " etc ...
     47   */
     48 
     49   /*
     50     ipt ranges from [0 to sz) and needs to be mapped to [0, 1)
     51   */
     52 
     53   return ((1.0*ipt)/sz)*(cmax - cmin) + cmin;
     54 }
     55 
     56 int fz(float* z, float* C, int* n){
     57   /*
     58     z ... z in f(z) = z^2 + C
     59     C ... C in f(z) = z^2 + C
     60     n ... current iteration
     61   */
     62   if(cmplxLenSq(z) < 4 && *n < iter_max){
     63     float reg[2]; //temporary register
     64     cmplxMult(reg, z, z);
     65     cmplxAdd(z, reg, C);
     66     (*n)++;
     67     fz(z, C, n);
     68   }
     69   return 0;
     70 }
     71 
     72 int* imgIters(int w, int h){
     73   /*
     74     w ... width or number of columns
     75     h ... height or number of rows
     76   */
     77   
     78   //Initialize array that contains the escape for each pixel initialized to 0
     79   int* data = (int*)malloc(sizeof(int)*w*h);
     80   for(int i = 0; i < w*h; i++) data[i] = 0;
     81 
     82   //for each pixel, calculate the Re-Im plane conversion then calculate escape count
     83   for(int i = 0; i < h; i++){
     84     for(int j = 0; j < w; j++){
     85 
     86       /*
     87         C + 0 points to 0 + 0i, C + 2 points to the pixel converted to complex coordinates and C + 4 points to the
     88         pre-selected constant for the Julia set.
     89       */
     90       float C[6] = {0, 0, convNtoR(j, w, vx_min, vx_max), convNtoR(i, h, vy_min, vy_max), julia_C[0], julia_C[1]};
     91 
     92       /*
     93         fractal_flag: 0 creates the mandelbrot set, otherwise julia
     94         I use a nifty little maneuver with boolean arithmetics to avoid using if-else statements
     95       */
     96       fz(C + 2*(fractal_flag != 0), C + 2 + 2*(fractal_flag != 0), data + i*w + j);
     97     }
     98   }
     99 
    100   return data;
    101 }