Just installed Whitebox 3.2.3 and I'd like to import a 14 MB.img file.
The data import options do not list .img as a file source.
A web search has also turned up nothing.
Their website is http://www.uoguelph.ca/~hydrogeo/Whitebox/download.shtml
Look at the toolbox here that says Data Import or Conversion Tools
You could try that. I have not tried or downloaded the software myself. You need to play it around or check the HELP on their software.