Computer Graphics

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Computer Graphics

• Graphics software allows users to create and edit
  graphics
• Graphics can be divided into 2 types
• Bitmap (Raster) Graphics
• Vector Graphics

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Bitmap Graphics

• A bitmap graphic is represented by a dot pattern
• Each dot is called a Pixel (picture element)
• A pixel has a single color only

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Vector Graphics

• A vector graphic is divided into objects
• Each object is defined by the method of drawing
  it

This picture contains 3 objectsa line, a circle
and a rectangle
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How to draw the circle?

• The circle is represented by a mathematical
  formula

Circle(50,100,150,black,1,green)
A few bits is enough to save the properties of
this circle!
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Advantages of using Vector Graphics

• It requires less storage space
• When a vector graphic is enlarged, it remains
  intact (no distortion)

Enlarging a Vector Graphic
The line is as smooth as before
Enlarging a Bitmap Graphic
The line thickened saw-tooth resulted
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Disadvantages of using Vector Graphics

• Vector graphics cannot look as realistic as
  bitmap pictures.

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Common Graphic File Format

• Bitmap (.bmp) - a common graphic file
  formatcan be read by almost all programs
• Gif (.gif) - a compressed bitmap file format. It
  can support up to 256 colors
• Jpeg (.jpg) - a lossy compressed bitmap file
  format. But it can support up to 16.7 million
  colors
• (because it applies lossy compression, some of
  the details is lost!)

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Jpeg Format (5kB)
Gif Format (26kB)
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Comparison Table
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Creating Graphics

• Painting Software
• Drawing Software
• Presentation Software

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Painting Software

• A painting program creates an image by setting
  the colors of individual screen pixels.
• The pictures created by a painting program are
  thus bitmap graphics.
• Example Paintbrush, PhotoImpact

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Drawing Software

• A drawing program generates formulae to represent
  the objects drawn by users. The pictures created
  are thus object-oriented graphics.
• In using a drawing program, you are provided with
  a variety of drawing tools.
• Example Corel Draw and Powerpoint.

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Presentation Software

• A presentation program is a drawing program that
  help users to prepare the essential components of
  a presentation - presentation outlines, slides,
  audience handouts and speakers notes.
• Users can also use a presentation program to run
  an on-screen slide show.
• Example Microsoft PowerPoint.

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Importing Graphics

• Clip Art Library
• Image Scanner
• Screen Capture

Outputting Graphics

• Printer
• Plotter