Introduction to Multimedia

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Introduction to Multimedia

• SMM 2005

2
Introduction to Multimedia

• Chapter 4

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Graphics Overview

• Key feature/element in multimedia products
• Most of the time, using text only is not enough
  to convey a message to the user.
• Multimedia products need attractive graphical
  combination and presentation
• Developers must understand the purpose and
  significance of graphics that are going to be
  used in their projects
• Also important in information delivery.

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Graphics Overview

• Graphics can be developed using several methods
• Illustration software
• Graphic/image manipulation software
• Acquiring through scanning or camera transfer
• Graphic files can be stored in various file
  format each format has different purposes

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4.1 Elements of Graphic

• To create a remarkable graphics, developer must
  understand graphics and its elements
• Lines
• Shapes
• Space
• Texture
• Color

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Lines

• A mark with length and directions
• Continuous mark made on some surface by a moving
  point
• Types of line include vertical, horizontal,
  diagonal, straight or ruled, curved, bent,
  angular, etc.

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Shapes

• Enclosed space defined and determined by other
  art elements such as line, color, value, and
  texture
• Can appear as 2 dimensional (2D) or 3 dimensional
  (3D)

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Space

• Refers to the distance or area between, around,
  above, below, or within things
• can be described as two-dimensional or
  three-dimensional as flat, shallow or as
  positive or negative space etc

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Texture

• Surface quality or "feel" of an object, its
  smoothness, roughness, softness, etc
• Actual or Simulated

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Texture

• Actual textures - can be felt with fingers
• Simulated textures - suggested by an artist in
  the painting of different areas of a picture

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Color

• Produced by light of various wavelengths - when
  light strikes an object and reflects back to the
  eyes

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Color

• An element of art with three properties
• hue or tint (the color name)
• intensity (purity and strength of a color)
• value (the lightness or darkness of a color)
• Photographers measure color temperature in
  degrees Kelvin (K).

Description Degrees Kelvin
Clear Blue Sky 8000 to 27,000
Rainy, Misty Daylight 7200 to 8500
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Graphics Image Development

• Graphical images obviously play a very important
  role in multimedia products
• Images may be photograph-like bitmaps,
  vector-based drawings, or 3D renderings
• Access to the right tools and right hardware for
  image development is important!
• E.g., graphic designers like to have large,
  high-resolution monitors or multiple monitors

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Graphics Image Development

• Still images are generated in two ways
• bitmaps (or raster-based)
• vector-drawn

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Generating still images Bitmap

• Bitmap - a matrix describing the individual dots
  that are the smallest elements (pixels) of
  resolution on a computer screen or printer

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Generating still images Bitmap

• Example

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Generating still images Bitmap

• Monochrome just requires one bit per pixel,
  representing black or white

BMP 16 KB
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Generating still images Bitmap

• 8 bits per pixel allows 256 distinct colors

BMP 119KB
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Generating still images Bitmap

• 16 bits per pixel represents 32K distinct colors
  (Most graphic chipsets now supports the full
  65536 colors and the color green uses the extra
  one bit)

BMP 234 KB
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Generating still images Bitmap

• 24 bits per pixel allows millions of colors

BMP 350KB
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Generating still images Bitmap

• More bits provide more color depth, hence more
  photo-realism,
• but require more memory and processing power
• Graphics production software may capture in
  24-bit color and convert to 8-bit

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Generating still images Bitmap

• GIF and PNG formats use a 8-bit color table
  allowing up to 256 color

GIF 74KB
PNG 63KB
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Generating still images Bitmap

• JPG preserves more color depth with 16 bits per
  pixel

JPG 19KB
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Generating still images Bitmap

• Bitmaps are best for photo-realistic images or
  complex drawings requiring fine detail

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Generating still images Bitmap

• Bitmaps picture and their suitability of use-
• Use the native Microsoft bmp format as a raw
  image that will later be processed. It faster to
  process.
• Use JPEG, for photo sharing on the web because of
  its size and quality.
• GIF is normally used for diagrams, buttons, etc.,
  that have a small number of colours
• It is also suitable for simple animation because
  it supports interlaced images.
• PNG is almost equal to gif except that it didnt
  support the animation format.

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How to Create Bitmap Graphics
Clip Art
Capture
Drawn
Scan
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Generating still images Vector-Drawn

• Vector-drawn - created from geometric objects
  such as lines, rectangles, ovals, polygons using
  mathematical formulas
• e.g., RECT 0,0,200,300,RED,BLUE says
• Draw a rectangle starting at 0,0 (upper left
  corner of screen) going 200 pixels horizontally
  right and 300 pixels downward, with a RED
  boundary and filled with BLUE.

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Generating still images Vector
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Generating still images Vector

• The first popular vector-drawn images were for
  computer-aided design (CAD)
• Such as AutoCAD, for aiding engineers and artists
  in creating complex renderings
• Graphic artists designing for print media use
  vector-drawn objects because they put rectangles
  and Bezier curves on paper without jaggies,
  exploiting high resolution printers

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Generating still images Vector

• Macromedia Freehand, Corel Draw Adobe
  Illustrator are vector-drawing applications
• Macromedia Flash puts vector-drawing on the Web
  with a plug-in

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3D Object

• 3D graphics tools, such as Macromedia Extreme3D,
  or Form-Z, typically extend vector-drawn graphics
  in 3 dimensions (x, y and z)

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3D Object

• A 3D scene consist of object that in turn contain
  many small elements, such as blocks, cylinders,
  spheres or cones (described in terms of vector
  graphics)
• The more elements, the finer the objects
  resolution and smoothness.

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3D Object

• Objects as a whole have properties such as shape,
  color, texture, shading location.
• A 3D application lets you model an objects
  shape, then render it completely.

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3D Object

• Modeling involves drawing a shape, such as a 2D
  letter, then extruding it or lathing it into a
  third dimension.
• extruding extending its shape along a defined
  path
• lathing rotating a profile of the shape around
  a defined axis

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Extrude and Lathe
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3D Object

• Modeling also deals with lighting, setting a
  camera view to project shadows

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3D Object

• Rendering produces a final output of a scene
  and is more compute-intensive.

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4.2 Colors

• The tools we use to describe color are different
  when the color is printed than from when it is
  projected.
• Projected color is additive.
• Printed color is subtractive.

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Additive Color

• The additive reproduction process usually uses
  red, green and blue light to produce the other
  colors.
• No light (or color) is black. All light (all
  colors) is white.

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Subtractive Color

• Subtractive color explains the theory of mixing
  paints, dyes, inks, and natural colorants to
  create colors which absorb some wavelengths of
  light and reflect others.

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4.2 Colors

• Color models
• Different ways of representing information about
  color
• Example
• RGB
• HSB
• CMYK

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HSB Model

• Based on human perception of color, describe
  three fundamental properties of color
• Hue
• Saturation (or chroma)
• Brightness - relative lightness or darkness of
  color, also measured as
• There is no HSB mode for creating or editing
  images

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HSB Model

• Hue - color reflected from or transmitted through
  an object, measured on color wheel

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HSB Model

• Saturation (or chroma) - strength or purity of
  color ( of grey in proportion to hue)

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HSB Model

• Brightness - relative lightness or darkness of
  color, also measured as

0
50
100
Black white
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RGB Model

• Add red, green and blue to create colors, so it
  is an additive model.
• Assigns an intensity value to each pixel ranging
  from 0 (black) to 255 (white)
• A bright red color might have R 246, G 20, B 50

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CMYK Model

• Based on light-absorbing quality of ink printed
  on paper
• As light is absorbed, part of the spectrum is
  absorbed and part is reflected back to eyes
• Associated with printing called a subtractive
  model
• Four channels Cyan (C ), magenta (M), yellow (Y)
  and black (K)

• In theory, pure colors should produce black, but
  printing inks contain impurities, so this
  combination produces muddy brown
• K is needed to produce pure black, hence CMYK is
  four-color process printing

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4.2 Color

• Color Gamut
• Range of colors that a color system can display
  or print
• Different models have different gamut (RGB has
  the smallest gamut, approximately)

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4.2 Color

• Color Channel
• Photoshop shows information about color elements
  in different channels
• E.g., RGB has at least three channels CMYK has
  at least four channels - at least, because
  Photoshop also permits Alpha channels for
  storing mask information
• A mask lets part of an image be transparent so
  that other layers show through

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4.3 Graphic Files Application Format

• Most popular formats
• JPEG (Joint-Photographic Experts Group)
• GIF (Graphical Interchange Format)
• PNG (Portable Network Graphic)
• Other formats
• BMP, PSD, TIFF/TIF, TGA, EPS, PCX, ICO

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JPEG

• For continuous tone images, such as full-color
  photographs
• Supports more than 16 millions of color (24-bit)
• Uses lossy compression (averaging may lose
  information)

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GIF

• For large areas of the same color and a moderate
  level of detail.
• Supports up to 256 colors
• Allows transparency and interlacing
• Uses lossless compression

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PNG

• lossless, portable, well-compressed storage of
  raster images
• patent-free replacement for GIF
• also replace many common uses of TIFF
• Support indexed-color, grayscale, and true color
  images an optional alpha channel for
  transparency

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Other Formats

• BMP Bitmap File Format.
• Native bitmap file format of the Microsoft
  Windows environment.
• PSD Photoshop Document.
• Native bitmap file format of the Adobe Photoshop
  graphical editing application.
• TIFF Tagged Image File Format.
• Used to exchange documents between different
  applications and platforms.

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Other Formats

• TGA Targa File Format.
• An image format designed for systems using
  Truevision video boards
• supported by MS-DOS platforms.
• EPS Encapsulated PostScript
• file format. Adobe drawing format supported by
  most illustration and page layout programs.

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Other Formats

• PCX ZSoft IBM PC Paintbrush file format.
• One of the oldest bitmapped formats popularized
  by MS-DOS paint programs that first appeared in
  the early 1980's.
• ICO Icon file format.
• Created by Microsoft for icons.

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4.4 Information Delivery

• Graphics are used to convey information in
  multimedia products.
• For example, a picture of an automobile engine is
  much more effective than text that merely
  describes it.

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4.4 Information Delivery

• Graphics for information delivery include
• Drawn images
• Charts and graphs
• Maps
• Scenery
• People

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4.4 Information Delivery

• In each case, the image must be relevant to the
  overall product.
• Image size, color in respect to the application
  and other images, and positioning must all be
  considered when using images.

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4.4 Information Delivery
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4.4 Information Delivery
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4.4 Information Delivery
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Summary

• The computer generates still images as bitmaps
  and vector-drawn images.
• Images can be incorporated in multimedia using
  clip arts, bitmap software, or by capturing,
  editing, or scanning images.
• Creating 3-D images involves modeling, extruding,
  lathing, shading, and rendering.
• Color is one of the most vital components of
  multimedia.