Overview of Graphic Systems Dr. Aree Ali Mohammed Assistant Professor 2014-2015 3rd Stage aree.ali@univsul.edu.iq University of Sulaimani – Computer Science Dept.

Computer Graphics and Vision Computer graphics are created using computers and, more generally, the representation and manipulation of image data by a computer with help from specialized software and hardware. Computer vision is a field that includes methods for acquiring, processing, analyzing, and understanding images.

What is Interactive Computer Graphics? User controls content, structure, and appearance of objects and their displayed images via rapid visual feedback Basic components of an interactive graphics system input (e.g., mouse, tablet and stylus, multi-touch…) processing (and storage) display/output (e.g., screen, paper-based printer, video recorder…)

Conceptual Framework for Interactive Graphics System/ GPU Application Model / database Software Hardware Application program Graphics Library - Graphics Library - Between application and display hardware there is graphics library / API. - Application Program - An application program maps all application objects to images by invoking graphics. - Graphics System – An interface that interacts between Graphics library and Hardware. - Modifications to images are the result of user interaction.

Graphics System Video Display Devices Refresh Cathode-Ray Tubes (CRTs) Raster-Scan Displays Random-Scan Displays Color CRT Monitors Flat-Panel Displays Graphics Workstations and Viewing Systems Input Devices Hard-copy Devices

Video Display Devices The primary output device in a graphics system is a video monitor. It is based on the standard cathode-ray tube (CRT) design. CRT : A beam of electrons, emitted by an electron gun, passed through focusing and deflection systems that direct the beam toward specified positions on the phosphor-coated screen  The phosphor emits a small spot of light at each position contacted by the electron beam  The light emitted by the phosphor fades very rapidly  the screen picture is maintained by directing the electron beam repeatedly over the same screen points  This type of screen called refresh CRT and the frequency is called refresh rate

Video Display Devices (CRT)

Video Display Devices (CRT)

Raster – Scan Systems  Most common type used in CRT, Based on television technology  The electronic beam is swept across screen, one row at a time, from top to bottom, each row is referred to as a scan line  As the electronic beam moves across a scan line, the beam intensity is turned on or off (or set to sum an intermediate value)  Picture definition is stored in a memory area called the refresh buffer or frame buffer

Architecture of Raster Scan

Architecture of Raster Scan

Architecture of Vector Scan

 Random – Scan Systems

Random – Scan Systems  Used in architectural and engineering layouts  Problem: no shading  Random-scan displays produce smooth lines  Raster-scan displays produce jagged lines

Color CRT Monitors  Use RGB color model  Produce more colors  Each pixel composed of three phosphor color dots (RGB)  3 electronic guns are used

Flat-Panel displays  Reduce volume, weight, and power  Thinner Plasma: Two glass plates with mixture of gases (neon)  Vertical conducting ribbons in one glass and horizontal in another

Liquid Crystal Display LCD Produce pictures by passing polarized light through liquid crystal material that can be aligned to either block or transmit the light Graphics Workstations and Viewing Systems Graphics systems range from small general-purpose computer systems with graphics capabilities to sophisticated full color systems that are designed specifically for graphics applications

Input and Hard Copy Devices Input Devices Keyboard and mouser |Trackball Joysticks Data glove Voice system early light pens to modern mice data tablet touch sensitive screens 3D input devices (spaceballs etc.) Button and dial boxes Output Devices Printers Pen plotter

Input and Hard Copy Devices Input Devices Keyboard - good for text, awkward for graphics. Mouse - popular and convenient for graphics. Data tablet - good for accurate digitalization of existing hard copies as vector sets. Scanner - - good for digitalization of existing hard copies as pixel sets. Light pen - usually not as convenient as a mouse. Touch screen - more useful for menu selection than for graphics. Joystick - useful for interactive graphics (games).

Output Device Raster Devices Vector Devices CRT - the common display device for personal computers. LCD - A smaller, lighter, lower power replacement for the CRT. LED - A smaller, lighter, lower power replacement for the CRT. Plasma screens - a more expensive but brighter alternative to LCDs. Printers - today's printers are good for both text and graphics Vector Devices Plotters - good for vector graphics. Oscilloscope - an early vector graphics output device

Review Questions and Discussion What do you mean by rasterization? Compare raster and vector scan displays. Write a short note on a. Flat panel display b. Plasma panel display 4. What do you understand by the terms raster scan and refresh rate? 5. Define aspect ratio.

Application of Computer Graphics  Graphs and Charts  Computer Aided Design CAD  Virtual-Reality Environments  Data Visualization  Entertainment  Image Processing  Graphical User Interfaces GUI  Advertisement  Games

Application of Computer Graphics

Graphics Software In computer graphics, graphics software or image editing software is a program or collection of programs that enable a person to manipulate visual images on a computer. Raster: http://en.wikipedia.org/wiki/List_of_raster_graphics_editors#List Vector: http://en.wikipedia.org/wiki/List_of_vector_graphics_editors

Reading List “Computer Graphics with OpenGL” , chapter 1, 2. Raster versus Vector http://www.sketchpad.net/basics1.htm