code: @Override
      public void loadImageThumbnail(final ImageView iv, String imageUrl, int dimension) {
          if (!TextUtils.isEmpty(imageUrl)) {
              Picasso.with(iv.getContext())
                      .load(imageUrl)
                      .resize(dimension, dimension)
                      .centerCrop()
                      .into(iv);
          } else {
              iv.setImageDrawable(null);
          }
      }
docs: region ImageGalleryAdapter.ImageThumbnailLoader Methods