depends JPEG &&
depends tiff &&

optional_depends LIBUSB \
                 "--enable-libusb" \
                 "--disable-libusb" \
                 "Enable libusb support" &&

optional_depends libgphoto2 \
                 "--with-gphoto2" \
                 "--without-gphoto2" \
                 "Enable libgphoto2 backend"

.