Ch13

• Computer graphics


  Generating 2D images of a 3D world represented in a computer
• Main tasks in Graphics

  • Modeling (shape): creating and representing the geometry of objects in the 3D world
  • Rendering (light, perspective): generating 2D images of objects
  • Animation (movement): describing how objects change in time
• Representations in Graphics


  • Vector Graphics: Image is represented by continuous geometric objects: lines, curves, etc.
  • Raster Graphics: Image is represented as a rectangular grid of colored pixels

  
• World Coordinates


  Center is (0,0)
• Screen Coordinates


  Upper-left corner is (0,0)
• Applications of Computer Graphics

  • Entertainment: animated movies, etc.
  • Medical Visualization
  • Educational Training
  • Game Modeling & Simulation
  • Graphical User Interfaces (GUI)
  • Computer Aided Design (CAD)
  • Scientific Visualization
• Other tasks in Graphics

  • Image processing techniques: Edge Detection, Image De-noising, Object Detection
  • Geometric Transformations: Translation, Rotation, Scaling, Clipping
  • More advanced operations: Hidden surface algorithms, Representing 3D shapes, Displaying depth relationships, Shading, reflection, ambient lighting
• Graphics Class in Java

  • paint() or paintComponent() is passed a reference to a Graphics object
  • A Graphics object is a device-independent interface to the computer's graphics display
  • Most of its methods are concerned with drawing shapes (filled and unfilled), and managing fonts and colours
• Put your own graphics on the screen

  1. Create your own paintable widget

  2. Put the widget on the frame

  3. Display it
• GUI component


  An object that can be represented visually on the computer screen and can be acted upon by a human user
• Rendering


  The process of transforming the GUI component's internal data into a visual image
• Graphics context object


  Holds the data needed to do the transformation of a GUI component's internal data into a visual image

  
• java.awt.Graphics


  The abstract superclass for all graphics context objects in Java

  
• Component Class


  • Superclass for many classes in java.awt package
  • Method paint() takes Graphics object as an argument
  • repaint() calls update(), which forces a paint() operation
• Class Color


  • Defines methods and constants for manipulating colors
  • Colors created from red, green, and blue (RGB) components
• JColorChooser


  Used to create a color chooser dialog box so that user can select any color
• showDialog() returns a Color object
• Class Font


  • States fonts, which are used to render text in a visible way
  • Constructor: creates a new Font from the specified font, and it takes three arguments: name, style, size
• Font Methods


  • getStyle()
  • getSize()
  • getName()
  • getFamily()
  • getFont()
  • isPlain()
  • isBold()
  • isItalic()
  • setFont(Font f)
• isItalic()


  Indicates whether or not this Font object's style is ITALIC

  
• setFont(Font f)


  Is used to set the graphics current font to the specified font
• Font


  Represents a font face, size, and style
• Font


  • BOLD
  • ITALIC
  • PLAIN

  
• Font types


  • Serif
  • Monospaced
  • SansSerif

  
• FontMetrics


  Has methods for getting font metrics
• g.getFontMetrics()


  Returns FontMetrics object
• Ascent


  The distance this string extends above the baseline
• Descent


  The distance this string descends below the baseline
• Leading


  The standard leading of the Font
• Height


  The standard height of a line of text in this font
• g.getFontMetrics(Font f)
• drawLine(x1, y1, x2, y2)

  Draws a Line from (x1, y1) to (x2, y2)
• drawRect(x1, y1, width, height)

  Draws a rectangle with upper left corner (x1,y1)
• draw3DRect(x1, y1, width, height, isRaised)


  Draws 3D rectangle, raised if isRaised is true, else lowered
• fill3DRect(x, y, width, height, raised)


  Paints a 3-D highlighted rectangle filled with the current color
• drawRoundRect(x, y, width, height, arcWidth, arcHeight)

  Draws rectangle with rounded corners
• fillOval(x, y, width, height)


  Fills an oval bounded by the specified rectangle with the current color

  
• drawArc(x, y, width, height, startAngle, arcAngle)

  Draws a circular or elliptical arc
• drawPolygon(xPoints[], yPoints[], points)


  Draws a polygon, with x and y points specified in arrays
• drawPolyline(xPoints[], yPoints[], points)


  Draws a polyline, a series of connected points