JuliaSet.java

/**
 * Julia set implementation.
 */
public class JuliaSet {
    private static final int WIDTH = 960;
    private static final int HEIGHT = 540;

    private static final int MAX_ITER = 200;

    // Complex constant c (choose different values for different styles)
    private static final double C_RE = -0.7;
    private static final double C_IM = 0.27015;

    private static final double X_MIN = -2;
    private static final double X_MAX = 2;
    private static final double Y_MIN = -1.2;
    private static final double Y_MAX = 1.2;

    private static final int BLOCK = 4;

    private static double mapX(int px) {
        return X_MIN + px * (X_MAX - X_MIN) / WIDTH;
    }

    private static double mapY(int py) {
        return Y_MIN + py * (Y_MAX - Y_MIN) / HEIGHT;
    }

    private static int juliaIter(double zr, double zi) {
        int count = 0;

        while (count < MAX_ITER) {
            double zr2 = zr * zr - zi * zi;
            double zi2 = 2 * zr * zi;

            zr = zr2 + C_RE;
            zi = zi2 + C_IM;

            if (zr * zr + zi * zi > 4.0)
                break;

            count++;
        }
        return count;
    }

    public static void main(String[] args) {
        StdDraw.setCanvasSize(WIDTH, HEIGHT);
        StdDraw.setXscale(0, WIDTH);
        StdDraw.setYscale(0, HEIGHT);

        for (int px = 0; px < WIDTH; px += BLOCK) {
            for (int py = 0; py < HEIGHT; py += BLOCK) {

                double zr = mapX(px);
                double zi = mapY(py);

                int iter = juliaIter(zr, zi);

                if (iter == MAX_ITER) StdDraw.setPenColor(StdDraw.BLACK);
                else StdDraw.setPenColor(StdDraw.WHITE);

                StdDraw.filledRectangle(px, py, BLOCK / 2.0, BLOCK / 2.0);
            }
        }
    }
}