=Paper=
{{Paper
|id=Vol-1324/paper_4
|storemode=property
|title=BrailleIO - A Tactile Display Abstraction Framework
|pdfUrl=https://ceur-ws.org/Vol-1324/paper_4.pdf
|volume=Vol-1324
|dblpUrl=https://dblp.org/rec/conf/tabletop/Bornschein14
}}
==BrailleIO - A Tactile Display Abstraction Framework==
https://ceur-ws.org/Vol-1324/paper_4.pdf
BrailleIO - a Tactile Display Abstraction Framework
Jens Bornschein
Human-Computer Interaction Research Group
Technische Universität Dresden
Nöthnitzer Str. 46, 01187 Dresden, Germany
jens.bornschein@tu-dresden.de
ABSTRACT more and more visual to expose their secrets. This way, in
In this paper BrailleIO, a small .NET framework for de- addition to purely text-based systems interactive visual and
veloping two-dimensional tactile applications, is presented. graphical user interfaces pose a big benefit for the most users
It offers general features for displaying tactile information but leave also some behind.
and for interaction. BrailleIO includes hardware abstrac-
tion, window and visualization features as well as basic inter- Visually impaired users rely on a substituting alternative
action functions, such as panning and zooming on different way to receive the information that is presented in a visual
content types. Information visualization can be organized in way. This mostly includes spatial information, too. While
several independent screens that can be divided into multiple the visual world is entering the third dimension in informa-
areas, having a full box model. Interaction can be realized tion presentation now, visually impaired people are getting
via hardware keys of the used device or by basic gestures if access to the second digital dimension with the help of the
the device is touch-sensitive. arisen smart mobile devices with touch screens. These are
well usable tools for easy and self-determined interaction.
Categories and Subject Descriptors But that is only audible in most cases. The step to a real
D.3.3 [Programming Languages]: Language Constructs tactile and, therefore, graphical interaction is still underrep-
and Features—classes and objects, data types and struc- resented.
tures, frameworks; H.5.2 [Information Interfaces and
Presentation]: User Interfaces—haptic I/O, input devices Because of so much graphical information, the growing re-
and strategies, Screen design, User interface management quest for two-dimensional dynamic tactile displays for blind
systems (UIMS); K.4.2 [Computers and Society]: Social computer users results in an increasing number of available
Issues—assistive technologies for persons with disabilities ideas and products. Several different designs and techniques
for refreshable tactile displays exist.
General Terms Many prototypes for building tactile displays were devel-
Documentation, Design oped, using different ideas to generate a dynamic tactile dis-
play [11, 12, 15]. Different approaches were used to gener-
Keywords ate tactile stimuli and arrange them in matrixes with more
Framework, tactile display, two-dimensional Braille display, or less resolution. The techniques range from mechanical,
pin-matrix device, hardware abstraction, standardization, electromagnetic, piezoelectric, or pneumatics, hydraulic or
tactile interaction, software development, tactile user inter- shape memory alloy based actuators up to surface changing
face polymers [8].
1. INTRODUCTION There are not only prototypes already available. Completely
Information technology is omnipresent in our daily life and functional systems built for solving application-specific prob-
we accept that because of so many benefits. With the in- lems are available. The Mimizu system, using the DotView-
creasing possibilities of information technology and the de- Pin-Display [5], is a stylus-pen based drawing workstation.
vices available everywhere getting more powerful, presenta- The pin display consists of 1,536 pins in a 48 x 32 pin-matrix
tion of data can get even more user friendly. In our visual with inter-pin space of about 3 mm and a display size of 144
world this means that rich applications and big data get by 96 mm. The application allows for painting and erasing
freehand structures or the presentation of small images.
Permission to make digital or hard copies of part or all of this work for With the GWP system [1], a small pin-matrix display of 16 x
personal or classroom use is granted without fee provided that copies 24 dots is used. The pin-matrix has a 3 mm pin raster, too.
are not made or distributed for profit or commercial advantage and that The device is portable and has 15 function keys, allowing
copies bear this notice and the full citation on the first page. Copyrights for for zooming, navigation and function calling. The GWP
third-party components of this work must be honored. For all other uses, device is used to give access to mathematics, especially to
contact the Owner/Author.
Copyright is held by the owner/author(s).
the graphical part.
TacTT ’14 , Nov 16 2014, Dresden, Germany.
Within the HyperBraille project the touch-sensitive device <> * BrailleIOScreen <>
BrailleIOMediator AbstractViewBoxModelBase
called BrailleDis was developed. Two generations of pin- * - view_ranges
- views + ViewBox
matrix devices exist, varying in body dimensions, amount + AdapterManager * + ContentBox
- content
of function keys and touch sensor resolution [13, 6]. The BrailleIOViewRange - content renderer
BrailleDis devices have a ten dpi dot matrix of 60 x 120 1
*
pins, resulting in a tactile area of 150 by 300 mm with 7,200 <>
<>
pins. The HyperReader software [10], using the BrailleDis IBrailleIOAdapterManager IBrailleIOAdapter
real hardware implementation
* * 1
devices for in- and output, was built to get access to desktop # Adapters
applications, such as office or web browsers on Windows sys-
tems. Thereby it offers different views on the content while Figure 1. Basic structure of BrailleIO.
keeping spatial layout information [9]. Within the Hyper-
Reader a region concept for tactile user interfaces is used
and evaluated as a well usable tool for structuring informa- application developers can use basic features without any
tion [7]. The architecture of the HyperReader software is knowledge of the used device or get access to required infor-
built to enable extensions and adaptations for different ap- mation through the framework.
plications. The software framework is big and hard to learn.
Furthermore, it is not free to use and cannot address other
tactile displays for in- or output.
2.1 General Overview - Structure
The framework is divided into two main parts. The first
part handles basic graphical elements and the generating of
As mentioned before, those products are often delivered with
output. The second is responsible for managing, modeling
their own proprietary software to visualize or retrieve in-
and implementing the real used hardware devices. As shown
formation. Developing a new software product, addressing
in Figure 1, the two parts are linked together by a so-called
those output devices, is a time-consuming and expensive
mediator (BrailleIOMediator). The mediator handles the
task. It could be hard for an application developer to con-
visibility and the rendering of the tactile user interface by
vey information through the original software on the output
managing different views which are building together the
device that is not related to the original purpose the system
resulting tactile output. Every important part of the frame-
was built for.
work should be accessible through this component.
In the following the framework BrailleIO is presented. Its
All modeled hardware devices - called adapters - have to
goal is to lower the obstacles and simplify the start for de-
be registered to the mediator. It distributes the generated
veloping applications for two-dimensional tactile displays by
tactile output to all registered and activated devices. The
giving basic tools for tactile user interface design and hard-
access to interaction events caused by user interaction with
ware modeling.
a device is not handled by the mediator. An interaction
handling process has to be connected directly to every sin-
2. THE FRAMEWORK gle registered adapter, which can be accessed through the
To reduce time and costs for developing a software applica- mediator.
tion that uses a tactile display as output device, the frame-
work BrailleIO is developed. It is a .NET 4 based software 2.2 Tactile User Interface
framework written in C# and, therefore, only usable for Win- The framework offers elements to build and structure tac-
dows operating systems. tile graphical user interfaces. The basic object for that is
the so-called screen (BrailleIOScreen). As shown in Fig-
A main goal of BrailleIO is to give basic implementations ure 1, a BrailleIOMediator can hold an unlimited set of
for common needed functions and structures when building screens. Normally, only one screen should be active at once
a tactile application. The barrier to enter should be as low and, therefore, will be rendered and sent to the displaying
as possible. The framework enables developers to achieve device. With this multiple screen metaphor it is possible
quick success without starting to solve fundamental prob- to implement and provide several different views or appli-
lems in the first place. The framework should give possi- cations simultaneously. The user can then switch easily be-
bilities for structuring information, presenting graphics and tween the different screens. A screen itself cannot have any
text - preferably as Braille - and enable interaction. content directly.
Successfully tested concepts, proven in previous projects [9, view-range screens
7], are used to build tactile user interfaces and bring them to
a wider field of users. The reuse of those concepts can help
to improve quality of tactile applications and can start to
bring consistency in structure as well as in look and feel of
such applications. Consistency is important, especially for
visually impaired users, because the user can rely on known
structures and interaction paradigms [2]. This can improve
learnability as well as efficiency and can reduce errors at the ViewBox
same time. content
Therefore, it seems to be necessary to idealize and abstract
the used hardware for input and output as well. This means, Figure 2. Screens and view-ranges.
width (ViewBox.Width) OffsetPosition.X
height (ViewBox.Height)
ContentHeight
OffsetPosition.Y
visible area
visible content of ViewBox
=
ContentBox
Padding
Border
Margin
ContentWidth
Figure 3. Box model of view-range and relation to
ViewBox. Figure 4. Relation between ViewBox, ContentBox
and content of a view-range.
As the arrangement of a two-dimensional tactile output into
several regions can support the bi-manual exploration of
information [9], the framework should allow this feature, be necessary to mark them as divided. Therefore, the box
too. Therefore, screens can be divided into several content model can be used even if only one of its parameters is ap-
areas (see Figure 2). Those areas are called view-ranges plied to create a border or a gap.
(BrailleIOViewRange). A screen consists of an unlimited
number of view-ranges (see Figure 1). Every view-range can A view-range is mainly characterized by the size and the
be independently filled with content, placed on the screen, position on a screen. These parameters are stored in the
sized, activated or deactivated. ViewBox member variable. In the ViewBox, the outer di-
mension of the view-range is defined as well as the x and y
The view-ranges are stored at the corresponding screen in position in relation to the top left corner of the correspond-
an internal list in the order they were added. This list repre- ing screen. The remaining visible area of a view-range is
sents a hierarchical, linear structure that has direct influence called ContentBox, which has the dimension of the View-
on the rendering process. The position inside the list cor- Box subtracting the several box model sections (see Figure
responds to a common z-index mechanism. This means an 4). All dimensions and positions used as parameters in this
overlapping view-range in a further position inside the list framework are defined in pins. Therefore, the definition of
overwrites an overlapped view of an earlier position. In ad- sizes and points is depending on the resolution of the used
dition, the definition of a layer order, not corresponding to output device.
the list order, is also possible by setting the z-index property
for the view-ranges. View-ranges are always opaque. That For handling oversized content and enabling the access to
means the underlying content will be erased by an overlap- content that doesn’t fit in a view-range, a panning concept
ping container, even if it is empty. is realized. With the parameter OffsetPosition the con-
tent can be moved under the view range frame. The offset
View-ranges have a full box model corresponding to the CSS position defines the start position of the content in relation
box model for web sites [14] (see Figure 3). The box model to the left corner of the ContentBox. If necessary, simple
consists of padding (space between content and border), a tactile scrollbars are added and rendered to give feedback to
border and a margin (free space around the border to other the user about the position inside the content. The scroll-
elements). Free space is defined as lowered pins which results bars consist of a continuous line with an adjacent indicator
in a recognizable gap between elements. A part of a border which is three points long and one point thick. To keep the
is rendered as a continuous straight vertical or horizontal scrollbar recognizable a one pixel space in the direction of
line of raised pins. Other border styles are not available the content is set up. Therefore, the scrollbars only reduce
until now. A border can be used to separate elements with the available content space by three pins.
a clear tactile stimuli. If a border is used, it is recommended
to set a margin and a padding as well to mark the separating A view-range can get several types of content to display. As
line as not related to the content. A border of one pin width shown in Figure 5 the basic data structure, to which every
seems to be sufficient in most cases. This also saves rarely other content type will be transformed, is a two-dimensional
available display space. All properties of the box model are Boolean matrix (bool[,]). A true-value represents a raised
independently definable in all four directions. pin on the tactile display, a false-value a lowered one. Other
content types are text, which is rendered in Braille or as
With these tools a screen can be organized in regions with an image, as well as pictures, which are rendered as binary
different content which can be separated by significant tac- images. With a free definable threshold for the lightness of
tile features, such as dividing space, separating lines or mark- a pixel, darker pixels will be set to raised pins and lighter
ing frames. The division of the available display space seems ones to lowered pins.
not always to be reasonable, especially on small displays
such as the GWP [1]. However, for displaying special, tem- In the end the framework allows for setting any other type
porary or non-persistent information the method of show- of content. However, this requires the definition of a spe-
ing brief overlapping view-ranges could be useful. To en- cialized renderer for the given content type, implementing
sure that contents of different areas are not mixed together the IBrailleIOContentRenderer interface, converting the
by recognizing them as one whole content area it seems to content to a usable Boolean matrix.
Text Image Other <> <>
BrailleIODevice
IBrailleIOContentRenderer IBrailleIOAdapter AbstractBrailleIO
BOOL BOOL + string AdapterType
+ int DeviceSizeX + bool Connected
AdapterBase
+ int DeviceSizeY + BrailleIODevice Device ...
+ bool HasKeys 1 + int DpiX + bool Synch
+ bool HasTouch + int DpiY ...
+ String Name ... Events:
Matrix bool[y,x] + int RefreshRate + void Synchronize ...
Events:
+ errorOccured
+ initialized
+ inputChanged
+ keyPressed BrailleIOAdapter_
+ keyStateChanged ShowOff
+ pinStateChanged
+ touchValuesChanged
Figure 5. Content types for view-ranges. Figure 6. Adapter and device class structure.
Nearly all renderer are hookable. This means, an exten- Some general device events are proposed as well (see Figure
sion or an user of the framework can get access to the ren- 6). These events should give feedback about availability and
derer functionality by registering a hook. This hook will changes in key-, touch- or pin-states as well as the occurred
be called before the renderer starts his work and after the errors. In these events the sending device and the original
renderer has rendered the result. A hook has the opportu- raw device data of the event are enclosed and sent to all
nity to manipulate all function parameters in the beginning registered listeners. The listener can decide if he wants to
of the rendering. Furthermore, the redering result can be handle the generalized data, such as the general buttons, or
modified before it will be returned and sent to the output the original device data, e.g. additional keys that are not
devices. This gives programmers the power to use already mapped to one of the general keys.
implemented standard renderer and adapt or extent them
to their needs, without implementing an own renderer. Two real hardware-specific adapter implementations were
built for different types of the BrailleDis series, named the
2.3 Device Abstraction BrailleDis 9000 [13] and the BrailleDis 7200 [6] (see Fig-
As mentioned before, the abstraction and modeling of hard- ure 8). In addition to the real adapter implementations,
ware is an essential part of the framework, too. Therefore, a software adapter was developed. The so-called ShowOff
the first idea was to identify basic properties and features. A adapter can be used for debugging if no real hardware de-
construct for modeling and mapping a real hardware inter- vice is available or for monitoring a connected BrailleDis
face was developed. In this, special properties are defined, device. It implements the IBrailleIOAdapter interface and
for instance, a proposed image refresh rate, the number of can be used as a standalone input or output device for ap-
pin-rows and columns or the availability of buttons or touch- plications based on the framework. It is inspired by the
sensitivity of the hardware device. BrailleDis 7200 device and can be used as emulator. With
the simulator it is also possible to enter single touch inputs
A specific hardware device still needs to be mapped to the by mouse.
proposed framework. For this purpose, an adapter has to be
provided that implements the IBrailleIOAdapter interface
and generates a unique device representation as an object of 2.4 Interaction
type BrailleIODevice (see Figure 6). This has to be done A set of basic functions for interaction are implemented. As
once for every new hardware device that should be used with mentioned before, a first assignment of keys with functions is
the BrailleIO framework. proposed by the adapter implementation (see section 2.3),
but not realized by the framework. The linking between
The implemented adapter is responsible to achieve proper buttons and functions has to be done by the application
access to the hardware device. This means the adapter has developer. Nevertheless, all necessary functions are available
the task to create, open and hold a channel to the hard- in a basic implementation.
ware device as long as needed and to bring the standard-
ized output-matrix on the device. At the same time, the
adapter implementation has to map the proprietary and device
IBrailleIOAdapter
device-specific interactions and events to the idealized data
models which are expected by the framework. If a device OK +
has hardware keys, they have to be modeled, too. Nine ba-
sic function keys are defined as a minimal set for a sufficient ESC
-
interaction on a touch-sensitive tactile graphic device (see
Figure 7). The key set consists of four navigation keys and GST
two zoom buttons to interact with oversized, graphical or
zoomable content, such as images. Furthermore, two inter-
action buttons for approval and refusal are defined. Finally,
a special key for touch-sensitive devices seems to be neces-
sary to start and stop a gesture input to avoid midas touch
effects [10]. Figure 7. General device model with nine keys.
BrailleDis 7200
set up devices
+ register to register
GST ESC
- Adapter device gesture
events recognizer
register
OK devices
set
the active real or virtual
device
AdapterManager adapt content
or views on
BrailleDis 9000 BrailleIOMediator user input
build screens
choose
active
add BrailleIOScreen add BrailleIOViewRange
screen
define size,
position, style
OK set content
ESC
+ and visibility
-
GST
Figure 8. General key mapping for BrailleDis 7200 Figure 9. Steps to set up a project with BrailleIO.
and BrailleDis 9000.
After setting up the device that should be used for in- and
Zooming can be realized by setting the zoom property of output, it has to be registered to the AdapterManager related
the corresponding view-range. The framework will handle to the BrailleIOMediator. A registration to the events
the zoomed rendering if possible. Panning operations can thrown by the device has to be done. If the device is touch
be connected to the OffsetPosition property of a view- sensitive, the optional basic gesture recognizer can be con-
range (see section 2.2). By setting the offsets to negative nected to interpret touch inputs. An unlimited number of
values the content can be moved below the visible area of devices can be registered but only one device can be marked
the view-range’s ViewBox (see Figure 4). Changing the y- as active. This device is used as main output. Other de-
offset realizes a vertical and changing the x-value a hori- vices can be used as output by setting the Synch property of
zontal scrolling. The offset can be changed freely. Several the AbstractBrailleIOAdapterBase. This leads the medi-
functions of the abstract base class implementation of the ator to mirror the tactile result to these devices. With this
view-ranges (see Figure 1) offer offset manipulation in an mechanism the ShowOff adapter can be used, for example,
easy manner. as debug monitor beside a real tactile matrix device.
A basic gesture recognizer is included. It recognizes a num- At least one view-range has to be defined for displaying con-
ber of basic gestures, such as pointing gestures (tab), swipes tent. It has to be configured with a position, size and the
(line), pinch, circle (half and full) and three finger drag op- optional box model. The view-range can be added to the
erations (compare [7]). All gestures are interpreted and mediator directly or it can be combined with other view-
returned with further information, such as start and end ranges in a screen which has to be added to the mediator.
point, direction or orientation. In addition, a timestamp An unlimited amount of screens are allowed. After setting a
fingerprint allows for the inference on the duration, speed or screen as active or visible it will be displayed on the output
temporary order of interactions. device. Every view-range has to get its own content which
will be rendered and presented. The views or the contents
Inversion and threshold adaption are also part of the frame- can be changed, for example, on user interactions reported
work for image handling. For instance, these features are from the device events.
useful for exploring images. Small sinks - regions of low-
ered pins inside an area of raised pins - can be transformed 3. CONCLUSION AND OUTLOOK
to a raised pin area for a better detection by inverting the The framework BrailleIO was presented. It enables a fast
presentation. The adaptation of the threshold level for the and easy entry into building applications on two-dimensional
binary image conversion allows for adjusting the presenta- tactile displays for visually impaired users. With the screen
tion to the given context. Especially if very light or very and view-range constructs a proper information organiza-
dark images are presented, the adjustment of the threshold tion and simultaneous reception is possible. The framework
is necessary to make structures visible at all. also proposes a hardware abstraction for pin-matrix devices
including general hardware keys and function binding.
2.5 Usage The framework is used, for example, as groundwork for a tac-
In the following a small guidance about how to set up a tile graphic production workstation called Tangram worksta-
project with the BrailleIO framework in a few steps is given tion [3]. This project enables collaborative work of a sighted
(compare Figure 9). and a blind user on one graphic.
Several open issues have to be solved and innumerable im- system for the blind using tactile displays and
provements are conceivable. At this point, there is no way ultrasonic pens - mimizu. In K. Miesenberger,
to map infinite further hardware keys to the generic key con- J. Klaus, W. Zagler, and D. Burger, editors,
struct. A continuous numbering of further keys could be a Computers Helping People with Special Needs, volume
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ing of these buttons. In this context, the implementation of 731–738. Springer Berlin Heidelberg, 2004.
more concrete hardware adapters would proof the concepts [6] D. Prescher. Redesigning input controls of a
and the portability beyond the BrailleDis devices. touch-sensitive pin-matrix device. In This Proceedings,
pages 19 – 24, 2014.
It is also unclear how to handle output devices with a sig- [7] D. Prescher, G. Weber, and M. Spindler. A tactile
nificantly higher resolution than 10 dpi, which will lead to windowing system for blind users. In Proceedings of
problems on rendering Braille. The resolution of an used the 12th International ACM SIGACCESS Conference
device is available in his specifications and therefore has to on Computers and Accessibility, ASSETS ’10, pages
be checked and used while rendering resolution dependent 91–98, New York, NY, USA, 2010. ACM.
content. [8] A. Richter and G. Paschew. Optoelectrothermic
control of highly integrated polymer-based mems
The next big and challenging step is the implementation applied in an artificial skin. Advanced Materials,
of a powerful Braille renderer. Currently, strings are ren- 21(9):979–983, 2009.
dered with an equidistant Braille font as an image and sent [9] M. Schiewe, W. Köhlmann, O. Nadig, and G. Weber.
to the output devices. There is no way back from the ren- What you feel is what you get: Mapping guis on
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example, for a controlled audio output of touched Braille Universal Access in Human-Computer Interaction.
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tactile screen-explorer. In K. Miesenberger, J. Klaus,
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further and better ideas. The framework is freely available
[11] R. Velazquez, E. Pissaloux, M. Hafez, and
through https://github.com/TUD-INF-IAI-MCI/BrailleIO.
J. Szewczyk. A low-cost highly-portable tactile display
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4. ACKNOWLEDGMENTS Virtual Environments, Human-Computer Interfaces
I thank Heinrich Kuhlmann for his work on BrailleIO, Dr. and Measurement Systems, 2005. VECIMS 2005.
rer. nat. Michael Schmidt for his implementation of a Proceedings of the 2005 IEEE International
basic gesture recognizer and Denise Prescher for her work Conference on, pages 6 pp.–, July 2005.
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