Understanding Image Types in Multimedia Applications

1. Graphics(image)Kuliah 06

2. Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : • Menunjukkan Penggunaan Gambar pada Aplikasi Multimedia

3. Outline Materi • What is an Image • Image Media Types • Bitmap Image • Vector Image • 3-Dimensional Graphic Models • Working With Graphics

4. 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

5. 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

6. 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.

7. 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

8. 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

9. 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

10. Bitmaps images Original image Shown magnified

11. 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)

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

13. 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

14. Advantages and Disadvantagesof 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

15. 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/

16. 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.

17. 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

18. 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

19. 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

20. Shown magnified Original image Scaling vector graphics

21. Advantages and Disadvantagesof 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

22. 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

23. 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

24. 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. X 3D model Y Z

25. 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

26. 3-Dimensional Graphic models

27. 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)

28. 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

29. 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

30. Converting image formats TrueType / PostScript Type font Bitmapped font Render as bitmap Text Bitmapped image Vector image Contour trace Optical Character Recognition (OCR)

31. 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

32. 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

33. 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.

34. Advantages and Disadvantagesof 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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