Embedding projector forces square aspect ratio

[wchargin]

Migrated from tensorflow/tensorflow#8610.

@jongchyisu says:

I tried to use tensorboard embedding visualization with sprite images.
It works well except two things:

1. Even though I set the image width and height as:
   embedding.sprite.single_image_dim.extend([my_width, my_height])
   and the projector_config.pbtxt file has:
   sprite {
   image_path: "sprite.png"
   single_image_dim: my_width
   single_image_dim: my_height
   }
   Tensorboard resizes the images to be square, though it can get correct part from the sprite image, except that:
2. Every last image of each row is not correct. This happens when I have lots of images (like 200 images with size 70*100).

Seems like it only support square images?

@appierys says:

I can confirm that indeed Tensorboard resizes the images to be square.

[dsmilkov]

Hi @jongchyisu,

Your observation is correct. 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.

Note that you can have non-square number of data points by having the last row in the sprite image be partially filled: see the sprite matrix example in the tutorial.

[canbakiskan]

If you want non-square sprites, you can fill the rest of the pixels with transparent values. See: #5149