Agenda. Programming Seminar. By: dr. Amal Khalifa. Coordinate systems Colors Fonts Drawing shapes Graphics2D API

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1 Agenda Coordinate systems Colors Fonts Drawing shapes Graphics2D API By: dr. Amal Khalifa 1 Programming 13:30 pm on Wednesday 9/4/2014 Location :

2 Painting components 2 Every component is responsible for drawing itself. If you want to use a standard component, you only have to add it to your applet or frame. You don t have to worry about painting it on the screen. That will happen automatically, since it already knows how to draw itself.

3 Painting components 3 Class JComponent (package javax.swing) contains a paintcomponent(graphics g) for drawing graphics. Not called directly; called only by the system when a lightweight Swing component needs to be repainted. Use the component s repaint() method instead. repaint() method returns immediately, without doing any painting itself.

4 Graphics Objects 4 A graphics context enables drawing on the screen. To do any drawing at all in JAVA, you need an object belonging to the class java.awt.graphics manages a graphics context and draws pixels on the screen Instance methods are provided in this class for drawing shapes, text, and images.

5 Graphics Contexts 5 To create a drawing surface: define a subclass of JPanel provide a custom paintcomponent(graphics g)method. the paintcomponentmethod must be smart enough to correctly redraw the component at any time A program should store state information in its instance variables decide what to draw. When the program wants to change the content of the component change the values of the relevant variables and call repaint().

6 6 Java coordinate system a scheme for identifying every point on the screen. x-coordinates from left to right. y-coordinates from top to bottom.

7 Graphics in java 7

8 Colors 8 JAVA is designed to work with the RGB color system. An RGB color is specified by three numbers that give the level of red, green, and blue, respectively, in the color. A color in JAVA is an object of the class, java.awt.color. Color class defines several named constants representing common colors

9 9 Color constants

10 10 Color-related graphics methods

11 JColorChooser Dialog 11 Package javax.swing provides the JColorChooser GUI component that enables application users to select colors. static method showdialog creates a JColorChooser object, attaches it to a dialog box displays the dialog. Returns the selected Color object, or null if the user presses Cancel or closes the dialog without pressing OK. Three arguments a reference to its parent Component, a String to display in the title bar of the dialog and the initial selected Color for the dialog.

12 Example 12

13 Fonts 13 A font represents a particular size and style of text. The available font names are system dependent, but you can always use the following four strings as font names: Serif, SansSerif, Monospaced, and Dialog. Example: Font plainfont = new Font("Serif", Font.PLAIN, 12); Font bigboldfont = new Font("Sans Serif", Font.BOLD, 24);

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15 Drawing Shapes 15

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21 Java 2D API 21 The Java 2D API provides advanced two-dimensional graphics capabilities for programmers who require detailed and complex graphical manipulations. For an overview, see the Java 2D demo visit download.oracle.com/javase/6/docs/technotes/guides/2d/ Drawing with the Java 2D API is accomplished with a Graphics2D reference (package java.awt). To access Graphics2D capabilities, we must cast the Graphics reference (g) passed to paintcomponent into a Graphics2D reference with a statement such as Graphics2D g2d = ( Graphics2D ) g;

22 Example 22 Class GradientPaint helps draw a shape in gradually changing. Graphics2D method fill draws a filled Shape object an object that implements interface Shape (package java.awt) method setstroke sets the characteristics of the shape s border.

Class GeneralPath 23 General path constructed from straight lines and complex curves (package java.awt.geom). Methods: moveto moves to the specified point.

23 Class GeneralPath 23 General path constructed from straight lines and complex curves (package java.awt.geom). Methods: moveto moves to the specified point. lineto draws a line from the current point to the specified point. closepath draws a line from the last point to the point specified in the last call to moveto. Graphics2D method translate moves the drawing origin to the specified location. Graphics2D method rotate rotates the next displayed shape. The argument specifies the rotation angle in radians (with 360 = 2p radians).

24 24 Thank you for attending!!

Java How to Program, 9/e. Copyright by Pearson Education, Inc. All Rights Reserved.

Java How to Program, 9/e. Copyright by Pearson Education, Inc. All Rights Reserved. Java How to Program, 9/e Copyright 1992-2012 by Pearson Education, Inc. All Rights Reserved. Overview capabilities for drawing two-dimensional shapes, controlling colors and controlling fonts. One of