Thanks, all. When I run convert -version, I get:
Version: ImageMagick 7.0.8-58 Q16 x64 2019-07-30 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2018 ImageMagick Studio LLC
Visual C++: 180040629
Features: Cipher DPC Modules OpenCL OpenMP(2.0)
Delegates (built-in): bzlib cairo flif freetype gslib heic jng jp2 jpeg lcms lqr lzma openexr pangocairo png ps raw rsvg tiff webp xml zlib
I realize that convert is based on IM 6, but I did install with the earlier versions check box ticked off.
convert logo: logo.gif
generates nothing--no warning, but also no product.
I also entered convert rose: NULL, which did nothing. Entering just convert rose generates an extended list of image setting options.
I am operating in Windows 10. The slash situation I agree is highly confusing but is a side-effect of R. My assumption (hope) is that tmap has been constructed properly to deal with those translations from R to the standard assumptions of the OS environment, being that others have successfully leveraged Image Magick through tmap. If that's the case, then the issue is probably still with how Image Magick is configured on my machine.