Full-screen magnification for windows using DirectX overlays

This paper presents the basic features of software-based magnifiers used by some visually impaired people to read information from a computer screen. The paper briefly presents two major approaches to full-screen magnification for modern multiple window systems (the paper focuses on Microsoft Windows). This paper describes in detail the architecture and operation of a full-screen magnifier that uses Microsoft DirectX Overlays. This approach leads to a robust magnifier that has a low computational overhead. The magnifier has problems with video cards that use a YUV color model but these problems may be addressed by RGB to YUV translation software - an issue that is still to be investigated. The magnifier also has problems when the generic device driver, rather than the manufacturer´s device driver, is installed on the system. The paper presents two further strategies for full screen magnification, namely, using multimonitor support and true type fonts for text enlargement.