code: private int adjustAlpha(int color, float factor) {
          int alpha = Math.round(Color.alpha(color) * factor);
          int red = Color.red(color);
          int green = Color.green(color);
          int blue = Color.blue(color);
          return Color.argb(alpha, red, green, blue);
      }
docs: Transparent the given color by the factor
  The more the factor closer to zero the more the color gets transparent
  
  @param color  The color to transparent
  @param factor 1.0f to 0.0f
  @return int - A transplanted color