Touchlib Homepage


touch img

What is Touchlib?

Touchlib is our library for creating multi-touch interaction surfaces. It handles tracking blobs of infrared light for you and sends your programs multitouch events, such as 'finger down', 'finger moved', and 'finger released'. It includes a configuration app and a few demos to get you started. It interaces with most major types of webcams and video capture devices. It currently works only under windows but efforts are being made to port it to other platforms.

Who Should Use Touchlib?

Touchlib only comes with simple demo applications. If you want to use touchlib you must be prepared to make your own apps. There are a few ways to do this. You can build applications in C++ and take advantage of touchlib's simple programming interface. Touchlib does not provide you with any graphical or front end abilities - it simply passes you touch events. The graphics are up to you. If you like, take a look at the example apps which use OpenGL GLUT.

If you don't want to have to compile touchlib, binaries are available.

As of the current version, touchlib now can broadcast events in the TUIO protocol (which uses OSC). This makes touchlib compatible with several other applications that support this protocol, such as vvvv, Processing, PureData, etc.. This also makes it possible to use touchlib for blob detection / tracking and something like vvvv or Processing to write appliactions. Of course the other option is to do all your blob detection and processing in vvvv or processing. It's up to you. Supporting the TUIO protocol also enables a distributed architecture where one machine can be devoted to detection and tracking and another machine can handle the application.

If you don't like touchlib and want to program your own system, the latest version of OpenCV (1.0) now has support for blob detection and tracking. This might be a good starting point.

My Mindmap

My mindmap for the touchscreen is available here. This contains info on what parts you'll need for the construction of the screen, where to find them and some very basic instructions for how to build a screen. It also includes some more links. I hope it's useful for some of the people reading this who are interested in doing their own screens. You'll need Freemind (which is coincidentally, free), in order to view it. I'm a big fan of freemind for planning out projects and getting ideas down. It's hierarchical nature allows you to organize and hide parts you are not interested in. It can also link to images, other mindmaps and web pages.


Frequently asked questions about the construction of the screen can be found here.

Where to get the source to Touchlib, our multitouch table library:

All our source code is available on our Google Code site at . You can acces the repsitory using Subversion. If you are using windows, get TortoiseSVN. Use Tortoise to access the repository and download all the files (much easier than going thru the web interface). If you are interested in porting touchlib to linux or the mac, please email me. The system was written in such a way that it should be easy to port and does not depend heavily on any windows specific api's.

Binaries are available here.

Touchlib is written in C++ (the BlobTracking / Analysis is all written by yours truly) and has a Visual Studio 2005 Solution ready to compile. No docs are available right now and it's windows only (though it should be possible to make everything compile under other OS's with a little work). It currently depends on OpenCV, DirectShow (you'll need the Microsoft Platform SDK), VideoWrapper and the DSVideoLib. The source code includes our main library which you can link into your application to start capturing touch events. It has support for most major camera/webcam types. It also includes a basic config app which will need to be run in order to calibrate your camera, and has a couple example apps. Alternately, I've heard other people have used things like vvvv, EyesWeb, processing and Max/MSP in order to do blob tracking / processing and make applications. You can check out some of the demo apps if you want to see how it works. Pong or the config app should be fairly easy to follow. Setting up a bare minimum multitouch app should only take a dozen lines of code or less.

DL Links for dependencies:

You'll need to configure a few environment variables to get everything compiled. They are:

  • DSVL_HOME - dsvideolib root directory
  • VIDEOWRAPPER_HOME - root directory of the video wrapper library
  • OPENCV_HOME - root directory of OpenCV
  • OSCPACK_HOME - root directory of oscpack

The config app

In order to calibrate the touchlib library for your camera and projector, you'll need to run the config app. Here's how it works. You'll need to set up your computer so that the main monitor is the video projector so that the app comes up on that screen. Run the config app. Press 'b' at any time to recapture the background. Tweak the sliders until you get the desired results. The last step (rectify) should just have light coming from your finger tips (no background noise, etc). When you are satisfied press 'enter'. This will launch the app in full screen mode and you'll see a grid of points (green pluses). Now you can press 'c' to start calibrating. The current point should turn red. Press on your FTIR screen where the point is. Hopefully a press is detected (you can check by looking in the debug window). Press 'space' to calibrate the next point. You'll continue through until all points are calibrated. Note that the screen may not indicate where you are pressing. When you are all done, you can press 'ESC' to quit. All your changes (slider tweaks and calibration points) are saved to the config.xml file. Now when you run any touchlib app it will be calibrated. Note that any changes to where the projector is pointing or your webcam will require a re-calibration.


Alternate config files are available if you want to test the library using an .AVI for input (instead of the webcam). Replace the config.xml with 5point_avi.xml or 2point_avi.xml. You can edit those files to use a different AVI if you like (you can record a new one using your camera - but you may need to tweak some of the other settings in the config too).


NEW: We now have an official community site for building FTIR tables. Access the site here . The site includes forums, a wiki, news and more.

Other tables and info.


IRC: #ftir on

posted on 2009-05-07 17:00 zmj 阅读(1235) 评论(0)  编辑 收藏 引用

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