7.6 掃描器

7.6.1 介紹

FreeBSD 就像任何現代作業系統一樣，都可以使用掃描器。 在 FreeBSD 是透過 Ports Collection 內的 SANE(Scanner Access Now Easy) 所提供的 API 來操作掃描器。 SANE 也會使用一些 FreeBSD 的驅動程式來控制掃描器硬體。

FreeBSD 同時支援 SCSI 和 USB 兩種介面的掃描器。在做任何設定之前，請確保 SANE 有支援您的掃描器。 SANE 有張 支援硬體 的清單，這裡有介紹掃描器的支援情況和狀態訊息。 在 uscanner(4) 內也有提供一份 USB 掃描器的支援列表。

7.6.2 Kernel 的設定

如同上述所提的 SCSI 和 USB 界面都有支援。這要取決於您的掃描器界面，而需要不同的設備驅動程式。

device usb
device uhci
device ohci
device uscanner

# kldload uscanner

uscanner_load="YES"

uscanner0: EPSON EPSON Scanner, rev 1.10/3.02, addr 2

device scbus
device pass

pass2 at aic0 bus 0 target 2 lun 0
pass2: <AGFA SNAPSCAN 600 1.10> Fixed Scanner SCSI-2 device
pass2: 3.300MB/s transfers

# camcontrol rescan all
Re-scan of bus 0 was successful
Re-scan of bus 1 was successful
Re-scan of bus 2 was successful
Re-scan of bus 3 was successful

# camcontrol devlist
<IBM DDRS-34560 S97B>              at scbus0 target 5 lun 0 (pass0,da0)
<IBM DDRS-34560 S97B>              at scbus0 target 6 lun 0 (pass1,da1)
<AGFA SNAPSCAN 600 1.10>           at scbus1 target 2 lun 0 (pass3)
<PHILIPS CDD3610 CD-R/RW 1.00>     at scbus2 target 0 lun 0 (pass2,cd0)

7.6.3 設定 SANE

The SANE system has been splitted in two parts: the backends (graphics/sane-backends) and the frontends (graphics/sane-frontends). The backends part provides access to the scanner itself. The SANE's supported devices list specifies which backend will support your image scanner. It is mandatory to determine the correct backend for your scanner if you want to be able to use your device. The frontends part provides the graphical scanning interface (xscanimage).

The first thing to do is install the graphics/sane-backends port or package. Then, use the sane-find-scanner command to check the scanner detection by the SANE system:

# sane-find-scanner -q
found SCSI scanner "AGFA SNAPSCAN 600 1.10" at /dev/pass3

The output will show the interface type of the scanner and the device node used to attach the scanner to the system. The vendor and the product model may not appear, it is not important.

Now we have to check if the scanner will be identified by a scanning frontend. By default, the SANE backends comes with a command line tool called scanimage(1). This command allows you to list the devices and to perform an image acquisition from the command line. The -L option is used to list the scanner device:

# scanimage -L
device `snapscan:/dev/pass3' is a AGFA SNAPSCAN 600 flatbed scanner

No output or a message saying that no scanners were identified indicates that scanimage(1) is unable to identify the scanner. If this happens, you will need to edit the backend configuration file and define the scanner device used. The /usr/local/etc/sane.d/ directory contains all backends configuration files. This identification problem does appear with certain USB scanners.

For example, with the USB scanner used in the Section 7.6.2.1, sane-find-scanner gives us the following information:

# sane-find-scanner -q
found USB scanner (UNKNOWN vendor and product) at device /dev/uscanner0

The scanner is correctly detected, it uses the USB interface and is attached to the /dev/uscanner0 device node. We can now check if the scanner is correctly identified:

# scanimage -L

No scanners were identified. If you were expecting something different,
check that the scanner is plugged in, turned on and detected by the
sane-find-scanner tool (if appropriate). Please read the documentation
which came with this software (README, FAQ, manpages).

Since the scanner is not identified, we will need to edit the /usr/local/etc/sane.d/epson.conf file. The scanner model used was the EPSON Perfection® 1650, so we know the scanner will use the epson backend. Be sure to read the help comments in the backends configuration files. Line changes are quite simple: comment out all lines that have the wrong interface for your scanner (in our case, we will comment out all lines starting with the word scsi as our scanner uses the USB interface), then add at the end of the file a line specifying the interface and the device node used. In this case, we add the following line:

usb /dev/uscanner0

Please be sure to read the comments provided in the backend configuration file as well as the backend manual page for more details and correct syntax to use. We can now verify if the scanner is identified:

# scanimage -L
device `epson:/dev/uscanner0' is a Epson GT-8200 flatbed scanner

Our USB scanner has been identified. It is not important if the brand and the model do not match. The key item to be concerned with is the `epson:/dev/uscanner0' field, which give us the right backend name and the right device node.

Once the scanimage -L command is able to see the scanner, the configuration is complete. The device is now ready to scan.

While scanimage(1) does allow us to perform an image acquisition from the command line, it is preferable to use a graphical user interface to perform image scanning. SANE offers a simple but efficient graphical interface: xscanimage (graphics/sane-frontends).

Xsane (graphics/xsane) is another popular graphical scanning frontend. This frontend offers advanced features such as various scanning mode (photocopy, fax, etc.), color correction, batch scans, etc. Both of these applications are useable as a GIMP plugin.

7.6.4 Allowing Scanner Access to Other Users

All previous operations have been done with root privileges. You may however, need other users to have access to the scanner. The user will need read and write permissions to the device node used by the scanner. As an example, our USB scanner uses the device node /dev/uscanner0 which is owned by the operator group. Adding the user joe to the operator group will allow him to use the scanner:

# pw groupmod operator -m joe

For more details read the pw(8) manual page. You also have to set the correct write permissions (0660 or 0664) on the /dev/uscanner0 device node, by default the operator group can only read the device node. This is done by adding the following lines to the /etc/devfs.rules file:

[system=5]
add path uscanner0 mode 660

Then add the following to /etc/rc.conf and reboot the machine:

devfs_system_ruleset="system"

More information regarding these lines can be found in the devfs(8) manual page.