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LECTURE 3 THE USES OF IMAGES IN MULTIMEDIA

LECTURE 3 THE USES OF IMAGES IN MULTIMEDIA. Prepared By Razia Nisar Noorani. 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. What is an image?.

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LECTURE 3 THE USES OF IMAGES IN MULTIMEDIA

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  1. LECTURE 3THE USES OF IMAGES IN MULTIMEDIA Prepared By RaziaNisarNoorani

  2. 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

  3. 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.

  4. What is an image? • 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

  5. What is an image? • Images play an important part in multimedia • Navigation • User interface components • Help systems • Clip art

  6. 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

  7. 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.

  8. 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

  9. 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

  10. 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

  11. Bitmapped images Original image Shown magnified

  12. 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)

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

  14. 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

  15. 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

  16. 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

  17. 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/

  18. 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.

  19. 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)

  20. 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?

  21. 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

  22. Scaling vector graphics Shown magnified Original image

  23. 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

  24. 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 Freehand http://www.adobe.com/products/illustrator/main.html

  25. 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,

  26. 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

  27. 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

  28. 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

  29. 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

  30. 3-Dimensional Graphic models

  31. 3-Dimensional Graphic models

  32. Hardware used to acquire images Flatbed scanner • 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

  33. Hardware used toacquire images Digital camera • 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

  34. Hardware used tocreate / 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

  35. Converting image formats Bitmapped font TrueType /PostScriptType 1 font Text Bitmapped image Vector image Render as bitmap Contour trace Optical Character Recognition (OCR)

  36. 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

  37. 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

  38. 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.

  39. 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

  40. 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.

  41. 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

  42. Next lecture... We will look at digital Audio formats

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