#include <math.h></math.h>

#include <helianthus.h></helianthus.h>

Animation anim = 0;

unsigned char pixels[512][512][4];

double r = 0.4, i = 0.6;

double mx, my, zmx, zmy;

double z = 1/128.0;

double cx = -2;

double cy = -2;

void setColor(double x, unsigned char *pixel) {

  double h0 = 240;

  double h1 = 0;

  double h = h0 + (h1 - h0)*x;

  pixelSet(pixel, colorByHSV(h, 1, 1));

}

void julia(double r, double i) {

  for(int y = 0; y < 512; ++y) {

    for(int x = 0; x < 512; ++x) {

      double rr = x*z + cx;

      double ii = y*z + cy;

      int b;

      for(b = 0; b < 64; ++b) {

        if (rr*rr + ii*ii > 4) break;

        double x = rr*rr - ii*ii + r;

        ii = 2*rr*ii + i;

        rr = x;

      }

      setColor(b/64.0, pixels[y][x]);

    }

  }

}

void fractal() {

  julia(r, i);

  imageToExistingGLTexture(animationGetGLTexId(anim), 512, 512, pixels);

}

void init() {

  anim = createAnimationFromImageEx(512, 512, pixels, FALSE, FALSE, FALSE, FALSE);

  fractal();

}

void draw() {

  double dt = worldGetFrameTime();

  int changed = 0;

  if (mouseDown("middle")) {

    r += (mouseX() - mx)*z/10;

    i += (mouseY() - my)*z/10;

    changed = 1;

  }

  if (mouseDown("left") || mouseDown("right")) {

    double k = pow(4, dt);

    if (mouseDown("left")) k = 1/k;

    cx += mouseX()*z*(1 - k);

    cy += mouseY()*z*(1 - k);

    z *= k;

    changed = 1;

  }

  mx = mouseX();

  my = mouseY();

  if (changed) fractal();

  fill(colorByName("white"));

  rectTextured(anim, 0, 0, 512, 512);

}

int main() {

  worldSetInit(&init);

  worldSetDraw(&draw);

  worldSetFrameRateEx(1, 100);

  worldRun();

}