save(ofn) saves the current qplot figure to the named file.
save(ext), where ext is just a filename extension (without the dot), uses the name of the current figure.
Optional argument dpi specifies bitmap resolution for png/jpeg output in pixels per inch. Alternatively, MMREO specifies bitmap resolution in pixels per millimeter. The default resolution is 300 dpi.
Optional argument qual specifies quality for jpeg output. (The default is 95.)