Lecture5 graphics

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LECTURE 5LECTURE 5

THE USES OF IMAGES IN MULTIMEDIATHE USES OF IMAGES IN MULTIMEDIA

Prepared ByPrepared ByRazia Nisar NooraniRazia Nisar Noorani

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Objective

What is an image?

The types of image Bitmap Vector

3D models

Hardware used to acquire / edit images

Converting from one format to another

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What is an image?

An image is the graphical and visual representation of some information that can be displayed on a computer screen or printed out

Images come in a variety of forms: Photographs Drawings Paintings Television and motion pictures Semantics Maps etc.

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Images show us the prominent features of the objects that they represent.

These images are composed quite differently, each is an effective representation of its subject

What is an image?

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What is an image?

Images play an important part in multimedia Navigation User interface components Help systems Clip art

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Image media types

Images can be generally divided into two formats: Bitmapped or raster images Vector graphics or Metafile images

Bitmapped images are stored as an array of pixels

Vector graphics are stored as the set of graphic primitives required to represent the image

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Bitmaps Image

A pixel is the smallest element of resolution on a computer screen (Screen Resolution)

A pixel is the basic unit of a digital images. Digital image is a picture that may be stored in, displayed on, processed by a computer.

As mentioned, bitmap is composed of a matrix elements called pixels

Each pixel can be in a specific colour and each pixel consists of two or more colors.

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Bitmaps Image

The range of these colours is known as the colour depth.

The color depth determined “How much data in bits used to determined the number of colors”.

Colour depth is measured in bits per pixel Remember: a bit (binary digit) is either 1 or 0 and

that there are eight bits in a byte

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Colour depth1 bit per pixel = 2 colours (monochrome)

2 bits per pixel = 4 colours

4 bits per pixel = 16 colours

8 bits per pixel = 256 colours

Generally good enough for colour images

16 bits per pixel = 65536 colours

Better quality for photograph-like images, also known as high colour

24 bits per pixel = >16 million possible colours

Used to recreate photo realistic images, also known as true colour

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Bitmaps Image

The more colours that are allowed per pixel, the greater the size of the image

The number of pixels is related to the size of file that required to store an image.

Remember, two factors effect the size file bitmap are: Resolution Color Depth

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Bitmapped images

Original imageOriginal image

Shown Shown magnifiedmagnified

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8bytesinsize

depthcolourheightwidth

Calculating the sizeof a raster image

Where: Width of the images measured in pixels Height of the images measured in pixels Colour depth is the number of bits used for color

measured in bits per pixel

Remember: 1024 bytes = 1 kilobyte (KB) 1024 kilobytes = 1 megabyte (MB)

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Example

A 640 x 480 pixel image in 24-bit colour would require how much disk space?

900KB

bytes9216008

7372800

8

24480640bytesinsize

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Popular bitmap formats

Microsoft bitmap (.bmp) Used in microsoft windows

TIFF - Tagged Image File Format (.tif) Used for faxing images (amongst other things)

JPEG - Joint Photographic Expert Group (.jpg) Useful for storing photographic images

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Popular bitmap formats

GIF - Graphics Interchange Format (.gif) Used a lot on web sites

PNG - Portable Network Graphics (.png) A new format for web graphics

PCD – Kodak photo CD A new format for store image in a compressed form

on a CD

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Advantages and Disadvantages of using bitmap images

Advantages Convey detail of information quickly Real life

Disadvantages Depend on a Resolution Effect to the image quality Size file is big

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Software to create bitmap images

Popular PC packages include: Microsoft Paint

Included with microsoft windows Microsoft PhotoDraw 2000

http://www.microsoft.com/office/photodraw/ Adobe Photoshop

http://www.adobe.com/products/photoshop/main.html Paint Shop Pro

http://www.jasc.com/psp6.html Macromedia Fireworks

http://www.macromedia.com/software/fireworks/productinfo/

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Vector images

Vector images are stored as the set of graphic primitives required to represent the image

A graphic primitive is a simple graphic based on drawing elements or objects such as shape

e.g. square, line, ellipse, arc, etc.

The image consists of a set of commands (mathematical equations) that are drawn the object when needed.

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Vector images

Storing and representing images by mathematical equations is called vector graphics or Object Oriented graphics.

Each primitive object has various attributes that go to make up the entire image

e.g. x-y location, fill colour, line colour, line style, etc.

Example: RECTANGLE : rectangle top, left, width, height, color

is ( 0, 0, 200, 200, red)

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Vector images

CIRCLE : circle top, left, radius, color LINE : Line x1, y1, x2, y2, color

Vector image or vector graphics can be resized without

losing the integrity of the original image.

Scaling a vector is a mathematical operation - only the attributes change, the image is unaffected

Q: Could you defined what the different between a digital image and Computer Graphics or graphics?

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Primitive geometric drawing objects

Basic Line Polyline Arc Bezier curve

Text Font, weight

Shapes Circle Ellipse Rectangle Square Pie segment Triangle Pentagon,

hexagon, heptagon, octagon, etc Tex tText

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Scaling vector graphics

Original imageOriginal image

V e c t o rg r a p h i c s

ShownShownmagnifiedmagnified

V e c t o rg r a p h i c s

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Advantages and Disadvantages of using vector image

Advantages Relatively small amount of data required to represent

the image. Therefore, it does not required a lot of memory to

store Easier to manipulate

Disadvantages Limited level of detail than can be presented in an

image

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Software to create vector images

Graphics programs are tools that allow an artist to create and edit designs used in multimedia applications.

Generally, graphics programs can be categorized as:• Drawing programs

– Creating draw type graphics– Provide freehand. Example geometric shape – Example : Adobe Illustrator, Corel Draw,

Macromedia Freehandhttp://www.adobe.com/products/illustrator/main.html

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Software to create vector images

Paint programs- Those creating bitmaps- useful in creating original art- Example: Paint Shop Pro

http://www.jasc.com/psp6.html

Image editing programs- Making changes to existing images, such as

manipulating the brightness or contrast, applying textures, patterns.

- Examples : Adobe Photoshop, Adobe Page Maker,

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Vector formats

Windows metafile (.wmf) Used by Microsoft Windows

SVG - Scalable Vector Graphics (.svg) A new format devised for the web

CGM - Computer Graphics Metafile (.cgm) Older format commonly used for clip art

Adobe PostScript (.ps) A page description language used to control printers

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Vector formats

Adobe Portable Document Format (.pdf) A page description language common on the web

Drawing Exchange Format (.dfx) Store 3D image created by design program AutoCAD

Encapsulated PostScript (.epf) Professional printing: Illustration program, Adobe Systems,

Desktop Publishing programs

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3-Dimensional Graphic models

A 3D model is a variation on the vector format

The location of a 3-dimensional object is specified using x, y and z co-ordinates

Further primitives can be found in 3D models

Cube, sphere, pyramid, etc. Camera, spotlight, texture, shading

etc.

3D model

XX

YY

ZZ

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3-Dimensional Graphic models

3D graphics offer the photorealistics effects that have you seen in TV, Computer Games

Examples, Motion Picture films such as: Jurassic Park, Terminator 2, Lost World and Toy Story

Examples 3D programs: Carigali Truespace 3D Studio Max Infini-D

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3-Dimensional Graphic models

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3-Dimensional Graphic models

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Hardware used to acquire images

Scanners and digital imaging products

Many forms of scanner Drum Flat-bed Negative / slide Hand-held

Important to check the optical resolution of the scanner

measured in dots per inch (DPI) Slide scanner

Flatbed scanner

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Hardware used toacquire images

Digital camera Uses digital memory instead of

film Images are transferred to

computer via a cable Can be very high resolution

Stills from a camcorder or PC “web-cam” type camera

Home products tend to be low resolution Web cam

Digital camera

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Hardware used tocreate / edit images

Graphics tablet and pen Preferred by digital artists Pressure sensitivity

Digitiser tablet Preferred by technical

artists Mouse has accurate

crosshair to help digitise drawings

Tablet and pen

Digitiser

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Converting image formats

Text

Text

Text

Text

Bitm

ap

ped

imag

eB

itmap

ped

imag

eB

itmap

ped

imag

eB

itmap

ped

imag

e

Vecto

r imag

eV

ecto

r imag

eV

ecto

r imag

eV

ecto

r imag

eBitmapped font

TrueType /PostScript

Type 1 font

Optical CharacterRecognition (OCR)

Contour trace

Render as bitmap

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Working With Graphics

Considerations and guidelines when we are working with graphics:

Choose the graphic depend on your work Choose the correct software Use minimum color depth Delivery Systems

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How graphics/images can be used effectively

Different types of graphics are used in different ways:

Line drawing are graphical representations of physical objects. There are 3 kinds of line drawings:

Isometric - represent 3-D objects without realistic perspective

Orthographic - are 2-D representations of objects

Perspective - represent objects in their most realistic form

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How graphics/images can be used effectively

Graphs and Tables

In just a glance, graphs can provide specific data, show general trends in data or depict the relationships between data and data trends

Diagrams

Help users conceptualize a process, flow or interrelationship. Examples of diagrams include: Flow charts, Schematic Drawings and Block Diagrams.

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Advantages and Disadvantages of using images

Advantages Convey a lot of information quickly Add visual simulation and colour Can communicate across language borders Enhance other media

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Advantages and Disadvantages of using texts

Disadvantages Do not provide in-depth explanations

Graphics rarely suffice to convey a whole message in business, technical or safety settings

Can be misinterpreted Graphics should be used carefully to make sure

the message is not ambiguous or cryptic.

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Summary

Today we have met the various types of image that are useful when creating multimedia applications

Pros and cons of bitmapped and vector images

What hardware is used to create each of these

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Next lecture...

We will look at digital Audio formats