docs: public static Bitmap drawShadow(Bitmap map, int radius) {
          if (map == null)
              return null;
  
          BlurMaskFilter blurFilter = new BlurMaskFilter(radius, BlurMaskFilter.Blur.OUTER);
          Paint shadowPaint = new Paint();
          shadowPaint.setMaskFilter(blurFilter);
  
          int[] offsetXY = new int[2];
          Bitmap shadowImage = map.extractAlpha(shadowPaint, offsetXY);
          shadowImage = shadowImage.copy(Config.ARGB_8888, true);
          Canvas c = new Canvas(shadowImage);
          c.drawBitmap(map, -offsetXY[0], -offsetXY[1], null);
          return shadowImage;
      }