Bug with large 2D images

[amirDahari1]

For some reason after pressing "confirm" there's a white screen. For example this nice image from René Rekers:

[rmdocherty]

Canvas.tsx, line 205 - add non null assertion for canvasRef before resizing

[rmdocherty]

Think I have addressed the root of this problem with commit in bug-fixes. There were two problems:

1. I assumed any RGB image was actually greyscale (i.e had same values for all 3 channels). To convert RGB images -> greyscale I used PIL's convert, which averages over the 3 channels - not a problem if all channels the same, but if they are different then the result of this conversion will be different to my frontend conversion, which only chooses the R channel of the image. This means the phase values are out of sync and causes indexing problems
2. My array preprocessing code on the backend only checked for (and therefore processed) RGB i.e 3 channel images. 4 channel images were ignored/treated as volumes

Still need to merge this to dev and then deploy onto app

[amirDahari1]

This makes a lot of sense, thanks for clarifying!