4 - Gambar

Matakuliah Tahun

: T0732 / Sistem Multimedia : 2007

Graphics Pertemuan 4

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: – – – – – –

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Photographs Drawings Paintings Television and motion pictures Semantics Maps, etc.

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

History

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Contact

Links

Promoted Bands

The Flairz

Little Birdy

The Waifs

John Butler Trio

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) Bina Nusantara

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 Bina Nusantara

Colour depth •

1 bit per pixel = 2 colours (monochrome)

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2 bits per pixel = 4 colours

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4 bits per pixel = 16 colours

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8 bits per pixel = 256 colours – Generally good enough for colour images

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16 bits per pixel = 65536 colours – Better quality for photograph-like images, also known as high colour

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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 True Colour (24 bits)

4 bits

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8 bits

1 bit

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

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 Bina Nusantara

Bitmaps images Original image

Shown magnified

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Calculating the size of a raster image width × height × colour depth size in bytes = 8 •

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

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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?

640 × 480 × 24 7372800 size in bytes = = 8 8 = 921600 bytes = 900KB

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Type of Compression Lossless 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 Bina Nusantara

Type of Compression Lossy 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

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

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

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

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

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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 Bina Nusantara

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/ Bina Nusantara

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. Bina Nusantara

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 Bina Nusantara

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 •

Basic – – – –

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Line Polyline Arc Bezier curve

Text – Font, weight

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Shapes – – – – – – –

Circle Ellipse Rectangle Square Pie segment Triangle Pentagon, hexagon, heptagon, octagon, etc

Scaling vector graphics Shown magnified

Original image

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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 Bina Nusantara

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.

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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 Bina Nusantara

Vector formats •

Windows metafile (.wmf) –

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SVG - Scalable Vector Graphics (.svg) –

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A page description language common on the web

Drawing Exchange Format (.dfx) –

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A page description language used to control printers

Adobe Portable Document Format (.pdf) –

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Older format commonly used for clip art

Adobe PostScript (.ps) –

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A new format devised for the web

CGM - Computer Graphics Metafile (.cgm) –

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Used by Microsoft Windows

Store 3D image created by design program AutoCAD

Encapsulated PostScript (.epf) –

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Professional printing: Illustration program, Adobe Systems, Desktop Publishing programs

3-Dimensional Graphic models • A 3D model is a variation on the vector format • The location of a 3dimensional object is specified using x, y and z co-ordinates X

• Further primitives can be found in 3D models – Cube, sphere, pyramid, etc. – Camera, spotlight, texture, shading etc. Bina Nusantara

3D model

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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 Bina Nusantara

Photorealistics Effects

Transformer the Movie (2007) Bina Nusantara

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) Bina Nusantara

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 “webcam” type camera – Home products tend to be low resolution

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Hardware used to create / edit images

Tablet and pen

• Graphics tablet and pen – Preferred by digital artists – Pressure sensitivity

• Digitiser tablet – Preferred by technical artists – Mouse has accurate crosshair to help digitise drawings

Digitiser Bina Nusantara

TrueType / PostScript Type font

Converting image formats

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Render as bitmap

Contour trace

Vector image

Text Optical Character Recognition (OCR)

Bitmapped image

Bitmapped font

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. Bina Nusantara

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 Bina Nusantara

Q&A

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