I want to print an image from a command line:
lp -o scaling=//100// image.jpg
How can I force it to be printed in grayscale?
Maybe you are looking for
lpoptions -l in order to know what's the name for your printer.
You can play it like thi (example with an HP Photosmart) :
lp -o scaling=//100// -oColorModel=KGray image.jpg
If you look in the PPD file for the current printer, you should get a hint of how to denote grayscale printing (or any option for that matter). It could be as above or
Try the following command to search the options for printers on your system:
grep -i gr[ae]y /etc/cups/ppd/*.ppd