[TensorBoard] How to make sprite images for the embedding projector?

Hi, I'm about to use the embedding projector for visualizing my own data but I can't. It's an issue like tensorflow/tensorboard#44 or same. In this issue, simply says:

We only support square sprite images and this limitation is imposed by our underlying WebGL texture implementation.Unfortunately, changing that requirement is a significant amount of work. It's much simpler to have the user generate square sprite images.

What "square" means? Each thumbnails must be squared? Total size of the sprite image must be square? Or both?

该提问来源于开源项目：tensorflow/tensorboard