code: public static Bitmap getBitmap(Drawable drawable) {
          if (drawable == null)
              return null;
  
          if (drawable instanceof BitmapDrawable) {
              return ((BitmapDrawable) drawable).getBitmap();
          } else {
              Bitmap bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(),
                      drawable.getOpacity() != PixelFormat.OPAQUE ? Config.ARGB_8888 : Config.RGB_565);
              Canvas canvas = new Canvas(bitmap);
              drawable.setBounds(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());
              drawable.draw(canvas);
              return bitmap;
          }
      }
docs: Drawable转换为Bitmap
  
  @param drawable
  @return