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MULTIMEDIA COMPONENTS
Graphics
Animation
Video
Audio
Cds
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GRAPHICS
A graphic is said to be worth a
thousand words if it is shown
when it is needed.
Graphics often combines text,
illustrations and colour.
Basically, there are 2 kinds of graphics :
• bitmaps (based on pixels)
• vector images (based on mathematical
equations)
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Graphic images
• A digital display is divided into
discrete, individually addressable
points called pixels
• Images are produced by
assigning a color and intensity to
each pixel
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Vector Graphics
• It is stored as a set of instruction which
describe the dimension and shape of
every component of the drawing
• To display a vector graphic, each
instruction is read and converted to the
shapes and colors that comprise the
image
• Created by any graphical programs can
have drawing tools (e.g Photoshop)
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Vector Graphics
• Advantages:
• Object orientation: objects in a
graphic can be manipulated
separately
• Good for line art and charts
• Disadvantages:
• The larger the graphic, the longer it
takes to render the image
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Bit Maps
• It is stored as a set of bits in
computer memory that define the
color and intensity of each pixel
in an image
• Created by digitizing images
(photo, art work) or using
Windows PAINT programs
(.bmp)
• Also called raster or pixel maps
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• Advantages:
• Can display faster than vector
graphics
• Good for reproducing images with
complex variations in color,
shading and detail
• Disadvantages:
• Require more disk space
• Fixed resolution can lead to
scalability problems
Bit Maps
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• Image depth refers to the maximal
number of colors used in bitmap
• Each pixel can have 1 or more bits of
color information attached to it
Image Depth
Bits Colors Uses
1 2 Text, line drawing
4 16 Simple drawings, graphics
8 256 Natural images
24 16.7M Photographic realism
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• Size (in bytes) = (Height x Width x
Color Depth) / 8
• Sample file size for different images
size and color depths:
• Monocrome: (640 x 480 x 1 bit)/8
= 38 KB
• 256 colors: (640 x 480 x 8 bits)/8 =
307 KB
• 16M colors: (640 x 480 x 24
bits)/8 = 922 KB
Image File Size
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• High quality images
• Big file size
• High resolutions
• Image requirement will affect
hardware and software selections
including authoring and graphic
software, video graphics adapter, disk
space and data transfer rate
Images : Issues
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Techniques for reducing image size:
• Reduce size of height and/or width
of image
• Reduce the number of colors (ex:
image depth)
• Image data compression
Image Compression
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• Data compression reduces file size by
eliminating redundancy
• Compression involves two parts :
compression and decompression
called codecs
• Two types of data compression:
• Lossless output is exactly the
same compression (used for
programs and data) (Example:
WinZip)
Image Compression
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• Second type of data compression:
• Lossy a set of data will undergo
a loss of accuracy after
compression. Typically used on
image or graphics, animation,
audio and video
• Eliminates info that is difficult for
our eyes to detect (Ex: eye is less
sensitive to change in color than it
is to change in intensity)
Image Compression
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• Bitmap (.bmp)
• Internal format used by Windows
• Graphics Interchange Format (.gif).
Used to transmit and exchange
images between platforms Joint
• Photographic Expert Group
(.jpg/.jpeg)
• Offers the greatest compression
(10:1 without visible loss)
Some graphic image formats
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Importance of graphic for education
We can communicate via graphics. It portrays our ideas
to our audience. Sharing graphics with them and
communicate with them can yield more information.
Graphics are used often in e-book (e.g. geography,
science, mathematics) to illustrate theories and
concepts.
Educational animation is important for explaining
subject matter that changes over time.
The use of graphics is to make reading materials more
interesting and easier to understand. However graphics
as educational aids, readers must be able to interpret
graphics correctly.
