ImageJ plugin: >8 bit data in a virtual stack cannot be projected

[melissalinkert]

See discussion in https://forum.image.sc/t/getting-exceptions-when-using-image-stacks-3d-project/119891.

The test steps are:

• open a file with Plugins > Bio-Formats > Bio-Formats Importer
• select Use virtual stack
• select Image > Stacks > 3D Project..., and click OK

If the original image is 8 bit, then this just works without error. If the original image is 16+ bit though, then an exception like this is expected:

java.lang.ClassCastException: class [S cannot be cast to class [B ([S and [B are in module java.base of loader 'bootstrap')
at ij.plugin.Projector.doOneProjectionY(Projector.java:622)
at ij.plugin.Projector.doProjections(Projector.java:396)
at ij.plugin.Projector.run(Projector.java:98)
at ij.IJ.runPlugIn(IJ.java:216)
at ij.Executer.runCommand(Executer.java:152)
at ij.Executer.run(Executer.java:70)
at java.base/java.lang.Thread.run(Thread.java:1583)

It looks like for some reason the virtual stack properties don't cause the 8-bit conversion to happen within the Projector plugin:

https://github.com/imagej/ImageJ/blob/master/ij/plugin/Projector.java#L276

It might be that VirtualImagePlus just needs to override getBitDepth():

https://github.com/imagej/ImageJ/blob/master/ij/ImagePlus.java#L1376

[imagesc-bot]

This issue has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/getting-exceptions-when-using-image-stacks-3d-project/119891/13