The main goal of this work was to develop an application which allows to connect the displays of multiple mobile devices for the purpose of showing images on a larger screen. These connected devices should form a group which allows to show selected images by splitting them up across the displays of group members. Particular challenges were the support of different display sizes and the provision of simple and intuitive means for adding new mobile devices to the group as well as for removing arbitrary devices from the group. Whenever the group changes, the displayed image should be automatically resized in order to adapt to the new size of the common screen.

In cooperation with NTS New Technology Systems GmbH, we have developed the Android application GrouPix, which meets the requirements stated above. Up to now, the following features have been implemented:

  • Connecting devices: Mobile devices can be connected with a simple one-finger gesture across their displays (see below). Similarly, a group of already connected devices can be joined by connecting the display of a new mobile device with that of a group member.
  • Sharing images: Allows to add images to the gallery, which will be instantly shared among all connected mobile devices. Depending on image size and wireless network connection, this may take some time.
  • Browsing images: Shared images can be browsed by swiping through the gallery with a simple two-finger gesture on any of the connected displays. The size of a displayed image is automatically adjusted to fill the whole resulting screen.
  • Adjusting images: Allows to move shared images on the common screen, or to zoom in and out of the images, by using simple two-finger gestures. These gestures can be performed on any display of the group.

In order to connect displays to a larger screen, each mobile device broadcasts messages with recognized touch gestures. These messages contain a timestamp and information about the direction of a touch gesture as well as its start- and endpoint on the display. Based on this information, it is possible to calculate for each device which part of an image it has to show on the commons screen. Thus, once a user swipes from one display to another as shown in the image below, the positions of these two touch gestures are related to recognize the relative positions of the displays to each other. The timestamps are used to determine the chronological order in which the gestures are performed.


Displays of mobile devices can be connected with a simple touch gesture from one device to the other.



  • The project website of GrouPix can be accessed at this link.
  • The Android application can be downloaded from the Google Play Store.



Jakob Grabner*, Christian Hofer*, Clemens Holzmann
Department of Mobile Computing, University of Applied Sciences Upper Austria, Austria
clemens.holzmann [at]

Doris Zachhuber
NTS New Technology Systems GmbH, Leonding, Austria
doris.zachhuber [at]

* … student in the Bachelor’s degree programme Mobile Computing