There are two categories of visual impairments. Individuals who are partially sighted (for example, blurred vision, near and far-sightedness, color blindness) and those who are totally blind. Assistive technologies are available for the Linux operating system for visually impaired users, and many of the software packages are free.
The following is a list of assistive technologies for visually impaired users:
Screen readers are software applications that are installed on the computer to provide translation of the information on the computer screen to an audio output format. The translation is passed to the speech synthesizer and the words are spoken out loud. Currently, fully functional screen readers are only available for Linux in console mode. This section describes some of the most common screen readers.
Emacspeak is the complete Audio Desktop is an excellent non-graphical, text based interface for users who are visually impaired. This application can be used as a screen reader in conjunction with a hardware synthesizer or IBM ViaVoice® Run-time text-to-speech application. More information and software packages of are available at: http://www.cs.cornell.edu/home/raman/emacspeak/. The Emacspeak HOWTO http://www.ibiblio.org/pub/Linux/docs/HOWTO/ includes a tutorial and installation guide.
Jupiter Speech System is a screen reader for Linux in console mode. A user guide and software packages are available at: http://www.eklhad.net/linux/jupiter/.
Screader is a screen reader for Linux in console mode that works with the Festival software speech synthesizer and the Accent hardware synthesizer. Information and downloads are available at: http://www.euronet.nl/~acj/eng-screader.html.
Speaker is a new plugin for the Konqueror file manager and Web browser. Speaker provides Text to Speech using the Festival speech system or IBM ViaVoice. Downloads are available at: http://dogma.freebsd-uk.eu.org/~grrussel/speaker.html.
Speakup is a screen review package for the Linux operating system. It requires a hardware speech synthesizer, such as the DecTalk Express. An installation boot disk and packages are available at: http://www.linux-speakup.org/ that allow a visually impaired user to install the Linux operating system.
ZipSpeak is a talking mini-distribution of Linux. More information and software packages are available at: http://www.linux-speakup.org/zipspeak.html.
Speech synthesizers can be a hardware device or a text to speech (TTS) software application that creates the sounds necessary to provide speech output. Hardware synthesizers are available for the Linux operating system; however, they can be very expensive and must be compatible with the screen reader application in order to function properly. The alternative is to download and install a software synthesizer such as IBM's ViaVoice or Festival and configure the application to a compatible screen reader, such as Emacspeak.
A hardware speech synthesizer is a device that is connected to the computer's serial or parallel port and translates the text to a spoken output. Normally there are Braille labels on all controls to indicate the off and on position, and volume control. Hardware synthesizers also have the ability to speak in different tones that can be setup to indicate various parts of a document or text. Some models will provide a connection for headphones. The following is a list of speech synthesizers that are supported on the Linux operating system and can be used with Emacspeak:
Accent SA and Apollo 2 (http://polio.dyndns.org/chip/vss.html)
DECTalk Express (http://www.4access.com/synthesizers.asp)
DoubleTalk (http://www.rcsys.com)
A software speech synthesizer is an application that translates the text on the screen to speech output and provides speech synthesis, so that the screen reader application can read information out loud to the user.
Festival is a general, multi-lingual speech synthesis system developed at the Center for Speech Technology Research (CSTR). It offers a full TTS system with various application program interfaces, as well as an environment for development and research of speech synthesis techniques. Mbrola or FestVox are needed to complete the Festival installation. Software packages and installation instructions are available at: http://www.cstr.ed.ac.uk/projects/festival/.
Mbrola is a speech synthesizer that can be used with a TTS application, such as, Festival to provide speech output. More information is available at: http://tcts.fpms.ac.be/synthesis/mbrola.html.
Screen magnifiers enable users that are partially sighted to view selected areas of the screen in a manner similar to using a magnifying glass.
GMag is a screen magnifier for X Windows. It provides continuous magnification while you work, as well as the option to change the contrast of images at run-time. More information and downloads are available at: http://projects.prosa.it/gmag/.
Puff is a screen magnifier for users who need a high magnification of text and graphics in X Windows. Puff follows the focus of the mouse or pointer and enlarges the portion of the screen under the cursor. In order for Puff to run properly on Linux the source code needs to be modified. This application is not a good option for inexperienced users. The software packages and source code modification instructions are available at: http://trace.wisc.edu/world/computer_access/unix/unixshare.html.
SVGATextmode enlarges or reduces the font size for users who perfer to work in console mode. The normal text screen that Linux provides is 80 characters across and 25 vertically. After SVGATextmode is installed, the text can be displayed much larger. One example would be 50 characters across and 15 vertically. The program does not offer the ablitity to zoom in and out, but the user can re-size when necessary. The most current download is available at: http://freshmeat.net/projects/svgatextmode/. Do not run try to run SVGATextmode from an X Windows terminal. You must be in console mode for the display to function properly.
UnWindows is a collection of programs that includes Dynamag, a screen magnification program that helps the user locate the mouse pointer. The source code is available for Dynamag as a stand alone application, or the entire UnWindows package can be downloaded at: http://www.cs.rpi.edu/pub/unwindows/. The entire UnWindows package will not work with Linux without programming modifications. However, the Dynamag application can be installed successfully without any additional code changes.
Xzoom is a screen magnifier similar to Xmag that allows the user to magnify rotate or mirror a portion of the screen. The most current download is available at: http://filewatcher.org/sec/xzoom.html.
The X Windows server can be setup with different screen resolutions. The ability to adjust the screen's resolution allows a partially sighted user to magnify the screen with a single key sequence. The steps to set up your system are as follows:
Changed directories, type cd /etc
Using a text editor, open the XF86Config file
Locate the line beginning with Modes and change it to
Modes "1280x1024" "1024x768" "800x600" "640x480" "320x240"
Note: The settings may vary based your monitor's highest resolution mode.
Save the file and exit.
To enlarge the text on the screen type Ctrl+Alt+keypad-plus and to make the text smaller type Ctrl+Alt+keypad-minus
Braille terminals are normally used by individuals who are totally blind and may be hearing impaired as well. A Braille display uses a series of pins to form Braille symbols that are continuously updated as the users changes focus. A Braille embosser is a hardware device for printing a hard copy of a text document in Braille. Braille translation software is required to translate the on-screen text to a Braille format.
The following Braille devices have been listed on the hardware compatibility list of one or more of the following Braille translation applications:
Braillex http://www.redhat.com/mailing-lists/blinux-announce/msg00031.html.
Alva B.V.: ABT3xx, Delphi (serial and parallel ports), Satellite. .
Baum: Vario/RBT 40/80 (emulation 1/2) http://www.baum.de/English/homeeng1.htm.
Blazie Engineering: BrailleLite 18/40 http://www.freedomscientific.com/index.html.
Handialog: VisioBraille 2040 http://www.handialog.com/indexuk.htm.
Handy Tech Elektronik GmbH: BrailleWave, mod20, mod40, mod80 http://www.handytech.de/.
MDV: MB208/MB408L/MB408S (protocol 5) http://www.cavazza.it/cnt/schede/scheda-mb408l-eng.html.
Pulse Data International: BrailleNote 18/32 http://www.pulsedata.co.nz/graphics.htm.
Telesensory Systems Inc.: Navigator 20/40/80 (latest firmware version only), PowerBraille 40/65/80 http://www.telesensory.com/.
Tieman B.V.: CombiBraille 25/45/85, MiniBraille 20, MultiBraille MB125CR/MB145CR/MB185CR http://www.braillevoyager.nl/uk/index.html.
Tiflosoft: VideoBraille 40 http://www.tinlecco.it/tiflosoft/.
The following Braille translation applications are available for download:
Brass is a new program that combines speech and Braille output. The current version is still in testing and can be downloaded at: http://www.butenuth.onlinehome.de/blinux/.
BrLTTY supports parallel port and USB Braille displays and provides access to the Linux console. It drives the terminal and provides complete screen review capabilities. It is available at: http://dave.mielke.cc/brltty/.
NFBTrans is a freeware Braille translator written by the National Federation for the Blind (NFB). Software packages are available for download at: http://www.nfb.org/nfbtrans.htm.
Changing the shape and size of the mouse cursor can help users who have a problem following or seeing the cursor. The X Big Cursor mini HOWTO explains how to configure enlarged mouse cursors with the X Windows system. This HOWTO is available at: http://www.icewalk.com/doclib/howtos/mini/X-Big-Cursor.html.
There are also a large select of cursors that can be downloaded at: http://themes.tucows.com/cursors.html.
Audio can be very useful to users who are visually impaired. In most X Windows desktop environments audio alerts and sound events can be setup within the desktop control center by enabling sound and verifying that the option to show sound is activated. You will need to check the desktop users manual for setup and configuration of sound events.
Locktones is an excellent application for providing toggle keys that sound an audio alert to warn the user that a keystroke has created a locking state such as Cap Locks, or Num Locks. The application can be downloaded at: http://leb.net/pub/blinux/.
Linux can also be configured to beep at the login prompt so the user knows when to type in the password. A configuration utility can be downloaded and installed that can provide this function at: http://leb.net/pub/blinux/bootmeup/.
Access Mozilla has a goal to build an accessible Web suite: browser, e-mail, news, composer and chat that conform to the W3C accessibility standards. More information is available at: http://access-mozilla.sourceforge.net/.
Blind + Linux = BLINUX provides documentation, downloads and a mailing list that focus on users who are blind. Information and software packages are available at: http://leb.net/blinux.
LaTex/Tex is an extremely powerful document preparation system and it can be used to produce large print documents. More information is available at: http://www.emerson.emory.edu/services/latex/latex_toc.html.
National Federation for the Blind's (NFB) purpose is to help blind persons achieve self-confidence and self-respect and to act as a vehicle for collective self expression by the blind. Information for blind users, as well as software are available at: http://www.nfb.org/.
Project Ocularis is run by volunteers, and the project's aim is to improve Linux accessibility through the creation of new free software and the modification of pre-existing free software. More information is available at: http://ocularis.sourceforge.net.
Screen is a standard piece of software that allows many different applications to run at the same time on a single terminal in console mode. Screen has been enhanced to support some Braille terminals directly. It is available for download at: http://www.icewalk.com/softlib/app/app_01508.html.
SuSE Linux is the first Linux distribution to support installation of the Linux operating system and applications that run on Linux in Braille. The Blinux screen reader runs in the background to enable visually impaired users to work in a Linux console environment. More information is available at: http://www.suse.de/us/products/susesoft/70news/new_in_70.html.
xocr is an optical character recognition program that scans written text, such as a book and translates it to audio output, so the information is available to visually impaired users. More information is available at: http://sal.unimedya.net.tr/Z/3/XOCR.html.