(anymap-xres anymap)
The procedures bitmap-xres, greymap-xres, graymap-xres and colormap-xres are aliases being bound to this primitive procedure for compatibilty.
The X-resolution of the anymap is returned as an inexact float (-1.0 if undefined or unknown).
> (define bitmap (bitmap-create 100 100))
bitmap
> (bitmap-xres bitmap)
-1.0