Just wanted to note, that for my Canon scanner, upon installing the drivers, only a
scangearmp2 application is installed, which looks nothing like the ScanGearMP screenshots from the accepted answer:
Upon clicking Version, this is displayed:
The worst thing about this, is that I get no "raw" image - I only get JPEG (and JPEG is embedded into the PDF too), with all the loss in quality and blockyness that entails.
other tools like Simple Scan or Xsane are not needed.
... well, if I had a driver connecting directly to Xsane, then I could get the raw image, and decide for myself how much loss of quality I want in my JPEG.
EDIT: It turns out for these versions of the drivers
scangearmp2-3.40-1-deb.tar.gz, on Ubuntu 18.04, I in fact do have a SANE back-end:
$ sudo sane-find-scanner
# sane-find-scanner will now attempt to detect your scanner. If the
# result is different from what you expected, first make sure your
# scanner is powered up and properly connected to your computer.
# No SCSI scanners found. If you expected something different, make sure that
# you have loaded a kernel SCSI driver for your SCSI adapter.
found USB scanner (vendor=0x138a, product=0x003f) at libusb:001:007
found USB scanner (vendor=0x04a9 [Canon], product=0x180b [MG3000 series]) at libusb:001:010
# Your USB scanner was (probably) detected. It may or may not be supported by
# SANE. Try scanimage -L and read the backend's manpage.
# Not checking for parallel port scanners.
# Most Scanners connected to the parallel port or other proprietary ports
# can't be detected by this program.
$ scanimage -L
device `pixma:04A9180B_62FF57' is a CANON Canon PIXMA MG3000 Series multi-function peripheral
simple-scan connects fine to it, and I scan 1200 dpi into a PNG, so all is good for me