bitmapTo8BitImage

bitmapTo8BitImage.java

    private byte[] bitmapTo8BitImage(Bitmap bitmap) {
        int[] pixels = new int[bitmap.getWidth() * bitmap.getHeight()];
        bitmap.getPixels(pixels, 0, bitmap.getWidth(), 0, 0,
                bitmap.getWidth(), bitmap.getHeight());

        ByteBuffer eightByteBuffer = ByteBuffer.allocate(pixels.length);

        for (int i = 0; i < pixels.length; i++) {
            int p = pixels[i];

            int red = Color.red(p);
            int green = Color.green(p);
            int blue = Color.blue(p);

            byte p1Rgb = (byte) (((int) Math.round(red / 255.0 * 7.0) << 5) |
                    ((int) Math.round(green / 255.0 * 7.0) << 2) |
                    ((int) Math.round(blue / 255.0 * 3.0)));

            eightByteBuffer.put(p1Rgb);
        }


        return eightByteBuffer.array();
    }