CMSHN1109 Multimedia

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LECTURE 5 THE USES OF IMAGES IN MULTIMEDIA
Prepared by Cik Nor Anita Fairos bt Ismail
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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

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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 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

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What is an image?

• 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
• 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

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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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Bitmapped images
Original image
Shown magnified
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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?

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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

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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

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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/produ
  ctinfo/

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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)

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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?
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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

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Scaling vector graphics
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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 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.ht
  ml

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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,

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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

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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

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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.

X
3D model
Y
Z
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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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3-Dimensional Graphic models
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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
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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
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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
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Converting image formats
Bitmapped font
TrueType /PostScriptType 1 font
Text
Bitmapped image
Vector image
Render as bitmap
Contour trace
Optical Character Recognition (OCR)
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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

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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.

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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

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Next lecture...

• We will look at digital Audio formats