read down-sampled stack in parallel

[raacampbell]

Can be very slow to load over the network. Should be faster if we parfor the loading.

[alexanderbrown]

Problem is that it's a single file so i'm not sure it can be parallelised. I'll take a look.

Not sure why it should be particularly slow over the network though?

[raacampbell]

At least with imread on a multi-page TIFF I know it's possible to read the individual pages in parallel. It's already done with a for loop so simply making it parfor should be sufficient.

[alexanderbrown]

I'll give it a go

[alexanderbrown]

Just had a quick look. It may work for files read using the imread approach, but most files need to be read using a Tiff object which won't easily work in parallel. I'll try a couple of things to get it to work