// We compress horizontally first, then vertically

// which I think may be the fastest way.

//

// Up to 7 pixel columns and 7 pixel rows may be discarded

// (those not fitting in an 8x8 block). The discarded pixels are

// along the right and bottom border of the image, respectively.

sclass FastDownscale8x8 {

  int w, h, w2, h2;

  int[] horizontallyScaledPixels, finalPixels;

  void scaleHorizontally(BufferedImage img) {

    scaleHorizontally(grabbableIntPixels(img));

  }

  void scaleHorizontally(GrabbableIntPixels gp) {

    int scaleX = 8, scaleY = scaleX;

    w = gp.w;

    int h = this.h = gp.h;

    int w2 = this.w2 = w/scaleX, h2 = this.h2 = h/scaleY;

    int[] newPixels = horizontallyScaledPixels = new int[w2*h];

    int iRow = gp.offset, iOut = 0;

    int[] pixels = gp.data;

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

      int iIn = iRow;

      for x to w2: {

        int r = 0, g = 0, b = 0;

        for subX to 8: {

          int rgb = pixels[iIn+subX];

          r += (rgb >> 16) & 0xFF;

          g += (rgb >> 8) & 0xFF;

          b += rgb & 0xFF;

        }

        iIn += 8;

        newPixels[iOut++] = rgbIntFullAlpha(r/scaleX, g/scaleX, b/scaleX);

      }

      iRow += gp.scanlineStride;

    } // for y

  }

  void scaleVertically {

    int scaleX = 8, scaleY = scaleX;

    int[] pixels = horizontallyScaledPixels;

    int[] newPixels = finalPixels = new int[w2*h2];

    int iRow = 0, iOut = 0;

    for (int y = 0; y < h2; y++) {

      int iIn = iRow;

      for x to w2: {

        int r = 0, g = 0, b = 0;

        int iIn2 = iIn;

        for subY to 8: {

          int rgb = pixels[iIn2];

          iIn2 += w2;

          r += (rgb >> 16) & 0xFF;

          g += (rgb >> 8) & 0xFF;

          b += rgb & 0xFF;

        }

        iIn++;

        newPixels[iOut++] = rgbIntFullAlpha(r/scaleX, g/scaleX, b/scaleX);

      }

      iRow += w2*scaleY;

    } // for y

  }

  BufferedImage get(BufferedImage img) {

    scaleHorizontally(img);

    scaleVertically();

    ret get();

  }

  BufferedImage get() {

    ret bufferedImage(w2, h2, finalPixels);

  }

}