sclass Image2B implements MakesBufferedImage {
  int w, h;
  byte[] pixels;
  
  *() {} // for persistence
  
  *(RGBImage img) {
    w = img.getWidth();
    h = img.getHeight();
    pixels = new byte[(w*h+7)/8];
    for y to h: for x to w:
      if (img.getPixel(x, y).getBrightness() >= 0.5f) {
        int i = y*w+x;
        pixels[i/8] |= 1 << (i & 7);
      }
  }
  
  *(BWImage img) {
    w = img.getWidth();
    h = img.getHeight();
    pixels = new byte[(w*h+7)/8];
    for y to h: for x to w:
      if (img.getPixel(x, y) >= 0.5f) {
        int i = y*w+x;
        pixels[i/8] |= 1 << (i & 7);
      }
  }
  
  // initializes with black
  *(int *w, int *h) {
    pixels = new byte[(w*h+7)/8];
  }
  
  RGBImage toRGB() {
    RGBImage img = new RGBImage(w, h, Color.black);
    for y to h: for x to w: {
      int i = y*w+x;
      if ((pixels[i/8] & (1 << (i & 7))) != 0)
        img.setPixel(x, y, Color.white);
    }
    ret img;
  }
  
  BWImage toBW() {
    BWImage img = new BWImage(w, h, 0f);
    for y to h: for x to w: {
      int i = y*w+x;
      if ((pixels[i/8] & (1 << (i & 7))) != 0)
        img.setPixel(x, y, 1f);
    }
    ret img;
  }
  
  BufferedImage getBufferedImage() { ret toBW().getBufferedImage(); }
  
  bool getPixel(int x, int y) {
    int i = y*w+x;
    ret (pixels[i/8] & (1 << (i & 7))) != 0;
  }
  
  void setPixel(int x, int y) {
    int i = y*w+x;
    pixels[i/8] |= 1 << (i & 7);
  }
  
  int w() { ret w; }
  int h() { ret h; }
  public int getWidth() { ret w; }
  public int getHeight() { ret h; }
}