Virtual Paper Keyboard Using OpenCV in Visual Studio

Piyush Arora


The project presented here uses a paper keyboard instead of an electronic keyboard as the input device. The paper keyboard, along with a webcam, forms a virtual keyboard. The virtual keyboard makes use of OpenCV software for video processing. The keyboard’s key characters are drawn on a white paper and a webcam is focused on it. You need to open a text editor such as Notepad. When you place your finger on a character on the paper keyboard, the character gets written in the text editor. The paper keyboard drawn on an A4-size white paper is shown in Fig. 1.

Fig. 1: Paper keyboard
Fig. 2: Typing the text on a virtual paper
Fig. 3: Setting the system variables

The advantages of this type of keyboard are its simplicity and wireless interface. Also, it is easy to use, because the user doesn’t have to press the keyboard but only touch the keys on the paper. The program output of virtual paper image (390×220 pixels) captured by the webcam is shown in Fig. 2.

Fig. 4: Screenshot of calibration window

Software program
The software is written in Visual C++. You need OpenCV software along with Visual Studio 2010 installed in your system.

OpenCV or Open Computer Vision, developed by Intel, is a set of tools used in image and video processing. To use this tool-set, you have to link the libraries with Visual Studio. OpenCV makes use of some simple functions to do the required processing.


  1. Is there any way I could fix this issue “First-chance exception at 0x00007FF973337788 in VirtualKeyboard.exe: Microsoft C++ exception: cv::Exception at memory location 0x0000002494EFF6B0.” over my vstudio


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