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A software based low vision aid

Authors
Publisher
University of Edinburgh
Publication Date
Keywords
  • Qa75 Electronic Computers. Computer Science
Disciplines
  • Computer Science
  • Design

Abstract

i Abstract The aim of the project was to design a Low Vision Aid using commercially available computing and/or entertainment hardware. The aid was designed primarily for the application of reading. A standard PC running Windows is the chosen platform for development. The design of a software application for scrolling enlarged text across a screen is presented. The problems of Line Tearing and slow rendering times from the PC display refresh were investigated. The Win32 GDI, OpenGL and DirectDraw graphics libraries were investigated for possible solutions to these problems. The final application was implemented using DirectDraw. ii Declaration of Originality I declare that this thesis is my original work except where stated. __________________________________________ iii Table of Contents Abstract i Declaration of Originality ii Table of Contents iii List of Tables vi List of Figures vii Glossary viii Conventions ix Chapter 1 Introduction 1 1.1 Aims 1 1.2 Motivation 1 1.3 Requirements 3 1.4 Project Planning 3 1.4.1 Research 3 1.4.2 Development 4 1.4.3 Trials 4 1.5 Report overview 5 Chapter 2 Background 6 2.1 Introduction 6 2.1.1 Macular Degeneration (MD) 6 2.1.2 Reading with macular degeneration 7 2.2 Reading Aids 8 2.2.1 Traditional LVAs 8 2.2.2 CCTV 9 2.2.3 Text to speech 10 2.2.4 PCs as Low Vision Aids 11 2.3 A PC based LVA: Motivation 11 2.3.1 LVA for computer use 11 2.3.2 LVA for reading only 12 iv 2.4 Summary 13 Chapter 3 Text Scroller Design 14 3.1 Introduction 14 3.2 Software Specification 14 3.2.1 A Generic Class Framework 14 3.2.2 Adapting The MFC Framework 15 3.3 Application Design in MFC 17 3.3.1 GDI 17 3.3.2 Formatting 17 3.3.3 Rendering onto display 18 3.4 Naïve Method for Scrolling 18 3.4.1 Rendering to memory (double buffering) 19 3.4.2 Protecting the buffer 19 3.5 Improved Methods for Scrolling 20 3.5.1 Alphabet Buffer Scrolling 20 3.5.2 Scrolling Window 21 3.6 Scrolling Text Implementation 22 3.6.1 CReaderDoc Initialisation 22 3

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