Graphics Programming

1
Graphics Programming
2
In this class we will cover

• Drawing lines, rectangles, and ellipses
• Copying an area
• Drawing an image

3
Drawing Lines, Rectangles and Ellipses

• Java2D oraganizes geometric shapes in OO fashion.
  There are classes to represent lines, rectangles
  and ellipses.
• Line2D
• Rectangle2D
• Ellipse2D
• These all implement the Shape interface

4
Drawing Shapes

• To draw a shape, you first create an object of a
  class that implements the Shape interface and
  then call the draw method of the Graphics2D
  class. Rectangle 2D rect . . .g2.draw(rect)
• There are two versions of each Shape class
• one with float coordinates (conserves memory)
• one with double coordinates (easier to use)
• ExampleRectangle2D rect new
  Rectangle2D.Double(10.0, 25.0, 22.5, 20.0)

5
Drawing Rectangles

• Rectangles are simple to construct
• Requires four arguments
• x- and y-coordinates of the upper-left corner
• the width and the height
• The Rectangle2D class has over 20 useful methods
  including
• get Width
• getHeight
• getCenterX
• getCenterY

6
Drawing Rectangles

• Sometimes you dont have the top-left corner
  readily available.
• It is possible to have two diagonal corners of a
  rectangle that are not the top-left corner and
  the bottom-right corner.
• To create a rectangle in this case use the
  setFrameFromDiagonal method.Rectangle2D rect
  new Rectangle2D.Double()rect.setFrameFromDiagona
  l(px, py, qx, qy)
• If you have a Point2D object, you can also create
  a rectangle by callingRectangle2D rect new
  Rectangle2D.Double(p1, p2)

7
Drawing Ellipses

• The class Ellipse2D is inherited from the same
  Rectangle class that Rectangle2D is.
• because of the bounding box surrounding the
  ellipse
• So, creating an Ellipse2D object is very similar
  to creating a Rectangle2D object.Ellipse2D e
  new Ellipse2D.Double(px, py, qx, qy)where px, py
  are the x- and y-coordinates of the top-left
  cornerand qx, qy are the x- and y-coordinates of
  the bottom-right cornerof the bounding box of
  the ellipse

8
Drawing Lines

• To construct a line, simple use the Line2D class.
• It too, requires 4 arguments (the x and y
  coordinates of the start and end positions)
• These coordinates can be 2 Point2D objects or 2
  pairs of numbers.Line2D line new
  Line2D.Double(start, end)
  orLine2D line new Line2D.Double(px, py, qx,
  qy)

9
Filling Shapes

• You can fill the interior of closed shape objects
  with a color.
• Simply call the fill instead of draw method on
  the Graphics object.Rectangle2D rect new
  Rectangle2D.Double(x, y, x2, y2)g2.setPaint(Colo
  r.red)g2.fill(rect)

10
Images

• You can display images on the Graphics object.
• You can use images stored locally or someplace on
  the Internet.
• If an image is stored locally callString
  filename Image image ImageIO.read(new
  File(filename))
• If an image is on the Internet, use the
  urlString filename Image image
  ImageIO.read(new URL(url)
• To draw the imageg.drawImage(image, x, y, null)

11
Copying an Area

• copyArea() method - Use to copy an area
• Requires 6 parameters
• x-coordinate and y-coordinate of the upper-left
  corner of the area to be copied
• Width and height of the area to be copied
• The horizontal and vertical displacement of the
  destination of the copy

12
More on Graphics

• We have just begun to touch on the various
  graphics shapes available. You can also draw
• arcs
• polygons
• three-dimensional shpes
• Java 2D also lets you create higher-quality
  two-dimensional graphics, images, and text using
• fill patterns such as gradients
• strokes that define the width and style of a
  drawing stroke
• anti-aliasing, a graphics technique for producing
  smoother on-screen graphics
• For more info see http//java.sun.com/docs/books/
  tutorial/2d/display/strokeandfill.html

13
Example

• So, lets put all of this together in an example
• Seehttp//www2.bc.edu/bernier/MC697/LectureNot
  es/DrawShapesTest.java