GraphicsPertemuan 4

Matakuliah : T0732 / Sistem MultimediaTahun : 2007

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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.

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What is an Image?

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

Opening Screen

Main Menu

Jazz Dive Profile Promoted Bands

JohnButlerTrio

TheWaifs

LittleBirdy

TheFlairz

History Contact

Links

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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 (mathematically defined)

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Raster Image• A pixel is the smallest element of resolution on a

computer screen (Screen Resolution)

• Bitmap matrix of pixel

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

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

• 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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Colour Depth

http://en.wikipedia.org/wiki/Color_depth

True Colour (24 bits) 8 bits

4 bits 1 bit

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Raster Image• More colour per pixel bigger image size

• 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 size of 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?

900KBbytes921600

87372800

824480640bytesinsize

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Type of CompressionLossless compression :• Modify the way the data is organized or

represented to reduce storage size.• No loss in detail;

Example: ‘Run-length Encoding’.• Original : AAABBBCCCCCCABCABC• RLE : 3A3B6C2ABC

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Type of CompressionLossy compression schemes:• Try to maximise compression without loss

obvious to human user.• Remove detail during the compression• NOTE: repeated compression caused loss in

quality

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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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Software to create raster

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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 vector

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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 modelXX

YYZZ

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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:– The Incredibles, Shrek, Happy Feet, Transformer, etc.

• Examples 3D programs:– Lightwave– 3D Studio Max– Maya

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Photorealistics Effects

Transformer the Movie (2007)

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Software to create 3D image

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3-Dimensional Graphic models

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Photorealistics Effects

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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

TextText

Bitmapped im

ageBitm

apped image

Vector image

Vector image

Bitmapped 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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Q & A