/******************************************************************************
 *  Compilation:  javac Swirl.java
 *  Execution:    java Swirl filename
 *
 *  Swirl image.
 *
 *  % java Swirl baboon.jpg
 *
 ******************************************************************************/

public class Swirl {

    public static void main(String[] args) {
        Picture pic1 = new Picture(args[0]);
        pic1.show();
        int width  = pic1.width();
        int height = pic1.height();
        double x0 = 0.5 * (width  - 1);
        double y0 = 0.5 * (height - 1);

        Picture pic2 = new Picture(width, height);

        // swirl
        for (int sx = 0; sx < width; sx++) {
            for (int sy = 0; sy < height; sy++) {
                double dx = sx - x0;
                double dy = sy - y0;
                double r = Math.sqrt(dx*dx + dy*dy);
                double angle = Math.PI / 256 * r;
                int tx = (int) (+dx * Math.cos(angle) - dy * Math.sin(angle) + x0);
                int ty = (int) (+dx * Math.sin(angle) + dy * Math.cos(angle) + y0);

                // plot pixel (sx, sy) the same color as (tx, ty) if it's in bounds
                if (tx >= 0 && tx < width && ty >= 0 && ty < height)
                    pic2.set(sx, sy, pic1.get(tx, ty));
            }
        }

        pic2.show();
    }



}