How to programmatically change contrast of a bitmap in android?

Here is complete method:

/**
 * 
 * @param bmp input bitmap
 * @param contrast 0..10 1 is default
 * @param brightness -255..255 0 is default
 * @return new bitmap
 */
public static Bitmap changeBitmapContrastBrightness(Bitmap bmp, float contrast, float brightness)
{
    ColorMatrix cm = new ColorMatrix(new float[]
            {
                contrast, 0, 0, 0, brightness,
                0, contrast, 0, 0, brightness,
                0, 0, contrast, 0, brightness,
                0, 0, 0, 1, 0
            });

    Bitmap ret = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), bmp.getConfig());

    Canvas canvas = new Canvas(ret);

    Paint paint = new Paint();
    paint.setColorFilter(new ColorMatrixColorFilter(cm));
    canvas.drawBitmap(bmp, 0, 0, paint);

    return ret;
}