code: public static int modulateColorAlpha(int color, int alpha) {
          int colorAlpha = color >>> 24;
          int scale = alpha + (alpha >> 7);
          int newAlpha = colorAlpha * scale >> 8;
          int r = (color >> 16) & 0xFF;
          int g = (color >> 8) & 0xFF;
          int b = color & 0xFF;
          return newAlpha << 24 | r << 16 | g << 8 | b;
      }
docs: Modulate the color to new alpha
  
  @param color Color
  @param alpha Modulate alpha
  @return Modulate alpha color