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Pertemuan 05Graphics

Matakuliah : T0553/Sistem Multimedia

Tahun : 2005

Versi : 5

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Learning Outcomes

Pada akhir pertemuan ini, diharapkan mahasiswa

akan mampu :• Menunjukkan Penggunaan Gambar pada

Aplikasi Multimedia

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Outline Materi

• What is an Image

• Image Media Types

• Bitmap Image

• Vector Image

• 3-Dimensional Graphic Models

• Working With Graphics

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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.

• 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– Draw-type or Vector graphics or Metafile images

• Bitmapped images are stored as an array of pixels. It represents the image as an array of dots, called pixels

• Vector graphics are stored as geometric shape 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 depth

• 1 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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Bitmaps 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

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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

• 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)

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

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Vector images

• 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

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Primitive geometric drawing objects

• Shapes– Circle– Ellipse– Rectangle– Square– Pie segment– Triangle– Pentagon,

hexagon, heptagon, octagon, etc

• Basic– Line– Polyline– Arc– Bezier

curve

• Text– Font,

weight 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 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 Freehand

– Paint programs• Those creating bitmaps• Useful in creating original art• Example: Paint Shop Pro

– Image editing programs• Making changes to existing images, such as manipulating the

brightness or contrast, applying textures, patterns• Examples : Adobe Photoshop, Corel PhotoPaint

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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

• 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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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)

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Hardware used to acquire 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

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Hardware used to create / 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 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

• 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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Galleri

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