is it implemented? (i need to modify only RGB->greyscale) scanimage --help seems to say so, but when i use it, i get $ scanimage --mode Grayscale --matrix-rgb 0,1,0,0,0,0,0,0,0 > sample scanimage: attempted to set inactive option matrix-rgb the sane-backends/backend/hp.TODO says > Find a way to set matrices in the frontend (gtk-table with sliders ?)