Can you give an example of a command this fixes? I've been fighting with trying to create mosiac images for a long time and I'm wondering if I had issues with this. Thanks.

CreateTiledMosaic -i t1w.nii.gz -o mosaic.png -t -1x-1 -p 5 -s 3 -d 2 -f 0x1

used to fail with something like

terminate called after throwing an instance of 'itk::ExceptionObject'
  what():  /build/ITKv5/Modules/IO/PNG/src/itkPNGImageIO.cxx:544:
PNG supports unsigned char and unsigned short

The way it's used in ANTs scripts always worked

CreateTiledMosaic -i t1w.nii.gz -o mosaic.png -r rgb.nii.gz -t -1x-1 -p 5 -a 0.5 -s 3 -d 2 -f 0x1

because the RGB overlay was used to compute an RGB pixel in the output, so the type conflict didn't happen.

Cheers, I already had sorted out a way to avoid this one when I don't have any overlay. This is nice to have solved.