Detect multi-page TIFF

[finetjul]

See #229 + data linked here

[manthey]

These files are being read by the tifffile tile source and are listing an axis of "I", which isn't one of Z, T, C, P (or XY).

[arjunrajlab]

Oh, I see. At least it is detecting an axis. Perhaps we just allow that axis to be specified by the user (default is Z).

[manthey]

See girder/large_image#957.

Ultimately, we need to do something extra when a file doesn't have its internal frames labelled with an appropriate axes.

The sample files are read with the tifffile source and report that they have 6 frames, but there is no indication of the axes (e.g., are they T, Z, XY, etc). The referenced PR allows this to be specified in the multi source's yaml/json file. For a given source, you can add framesAsAxes: {<axis1>: <stride1>, <axis2>: <stride2>, ...}. For this case, for instance, this might be framesAsAxes: {z: 1} to indicate that the frames are the z axis.

We could do fancier things where an image with unlabelled axes contains two things (e.g., channel and z-stack), then that framesAsAxes would specify a stride for each of those axes.

@luciemac Once the associated large_image PR is merged, we'll need to add the appropriate frameAsAxes to the multi-source's file IF the source image doesn't have at least one of IndexC, IndexT, IndexZ, IndexXY.