1. 2 Computer Graphics and Vision What is Interactive Computer Graphics? User controls content, structure, and appearance of objects and their displayed.

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Overview of Graphic Systems

Dr. Aree Ali Mohammed Assistant Professor2014-20153rd [email protected]

University of Sulaimani – Computer Science Dept.

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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.

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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…)

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Conceptual Framework for Interactive Graphics

GraphicsSystem/

GPUApplicationModel / database

Software Hardware

Applicationprogram

GraphicsLibrary

- 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.

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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

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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

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Video Display Devices (CRT)

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Video Display Devices (CRT)

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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

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Architecture of Raster Scan

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Architecture of Raster Scan

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Architecture of Vector Scan

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Random – Scan Systems

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Random – Scan Systems

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

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Color CRT Monitors

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

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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

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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 systems range from small general-purpose computer systems with graphics capabilities to sophisticated full color systems that are designed specifically for graphics applications

Graphics Workstations and Viewing Systems

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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

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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).

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Output Device

Raster DevicesCRT - 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 DevicesPlotters - good for vector graphics.

Oscilloscope - an early vector graphics output device

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Review Questions and Discussion

1. What do you mean by rasterization?2. Compare raster and vector scan displays.3. Write a short note on

a. Flat panel display b. Plasma panel display4. What do you understand by the terms raster scan and refresh rate?5. Define aspect ratio.

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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

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Application of Computer Graphics

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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

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Reading List

“Computer Graphics with OpenGL” , chapter 1, 2.

Raster versus Vector

http://www.sketchpad.net/basics1.htm