1. eleventh
Graphics in Java

2. Notes on SimpWin example
Because of the inheritance mechanism, we can say that a SimpWin object is a JFrame object, just as we can say that, for example, a Labrador Retriever is a dog
SimpWin is just a specific type of JFrame
The first line in the main method is worth noting: we are creating an instance of the class we’re defining
We have to do this because of the nature of main – it is a static method, and, therefore, exists independent of any SimpWin object – so we have to give it an object to work with
The rest of the code in main() consists of instructions that set up the window to be displayed – this sort of functionality usually appears in a class’s constructor, as in the next example

3. Simple window example import javax.swing.*;
public class SimpWin extends JFrame {
public static void main (String [] args) {
SimpWin sw = new SimpWin();
sw.setSize(300,200);
sw.setTitle("Simple window");
sw.setLocation(150, 150);
sw.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
sw.setAlwaysOnTop(true);
sw.setVisible(true); }

4. Example, part 2 import javax.swing.*;
public class SimpWin2 extends JFrame {
public SimpWin2 () {
setSize(300,200);
setTitle("Simple window, part deux");
setLocation(150, 150);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setAlwaysOnTop(true);
setVisible(true); }
public static void main (String [] args) {
SimpWin2 sw = new SimpWin2();

5. Notes on second part of example
The second example is just like the first, except:
we have explicitly defined the constructor, which contains all of the code that describes the object to be created
we have limited main() to a simple call to the constructor; main() exists just as a tester method for the rest of the class
Note the method call syntax within the constructor – we call the methods without an apparent calling object or class
In fact, the calling object is the object being created by the constructor

6. A more interesting window
We can now create a blank window, but we want to be able to draw pictures
The JFrame class includes a method (inherited by any of its child classes) called paint(), which enables us to use the window as a blank canvas on which we can place shapes and colors
The shapes and colors are controlled by an instance of a class named Graphics, which is passed to paint() as an argument

7. Drawing pictures with Java
Java’s Graphics class contains methods for drawing lines and simple geometric figures (e.g. rectangles, ellipses)
Figures can be hollow or filled with color
Drawings are created within the context of an X-Y coordinate system illustrated on the next slide

8. Drawing pictures with Java
Java’s Graphics class contains methods for drawing lines and simple geometric figures (e.g. rectangles, ellipses)
Figures can be hollow or filled with color
Drawings are created within the context of an X-Y coordinate system illustrated on the next slide

9. Java screen coordinate system

10. Java coordinate system and graphics objects
As the previous slide illustrates, the origin point (0,0) is in the upper lefthand corner of the screen (or Container, such as a JFrame )
The X axis is horizontal and the Y axis is vertical; all values are positive
A figure, such as a rectangle or ellipse, has a bounding rectangle that indicates the borders in which it is drawn in the space
The upper left corner of this position and the size of the figure are specified in its constructor

11. Swing objects and the paint() method
Most Swing components include a paint() method, which is used to draw the component on the screen
This method is inherited from JComponent, an ancestor class for most of the Swing objects
As an inherited method, we have been able to use it (invisibly, since none of our code has called it directly) without modifying, or overriding the original version
In order to draw our own pictures, we will need to provide a new paint() definition, overriding the original

12. The paint() method
The paint method for an object is automatically invoked when the object is made visible; there is almost never an explicit call to the method
The paint() method has a single parameter of type Graphics, typically named g
We use g to invoke the methods that draw pictures
The Graphics class is defined in the awt package, which means we need another import statement if we want to add a paint method to our code

13. Example import javax.swing.*; import java.awt.*;
public class BlueSquare extends JFrame {
public BlueSquare () {
setSize(140,160);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true); }
public void paint (Graphics g) {
g.setColor(Color.BLUE);
g.fillRect(20,40,100,100);
public static void main (String[] args) {
BlueSquare b = new BlueSquare();

14. Learning Goals Understand at a conceptual and practical level
How to draw more simple shapes with java.awt.Graphics
Arcs
Rectangles
Bitmapped pictures versus vector graphics
How to use a java.awt.Graphics2D class
How to convert the Graphics class to it
How to set the color
How to set the paint
How to set the stroke (paint brush)
How to create the object to be painted
How to paint the object

15. Drawing Arcs Arcs Outlined Arc Filled Arc
g.drawArc(topLeftX, topLeftY, width, height, startAngle, arcAngle);
Filled Arc
g.fillArc((topLeftX, topLeftY, width, height, startAngle, arcAngle);
The top left x and y in the ovals and arcs are for the top left corner of the bounding rectangle.
The arcAngle is the amount to add to the startAngle to get the endAngle.

16. Georgia Institute of Technology
Drawing Rectangles
Rectangle
Outlined Rectangle
g.drawRect(topLeftX, topLeftY, width, height);
Filled Rectangle
g.fillRect(topLeftX,topLeftY,width,height);
Outlined Rounded Rectangle
g.drawRoundRect(topLeftX,topLeftY,width,height,arcWidth,arcHeight);
Filled Rounded Rectangle
g.fillRoundRect(topLeftX,topLeftY,width,height,arcWidth,arcHeight);
The topLeftX and topLeftY are the coordinates of the top left point of the enclosing rectangle for the rounded rectangle.
The arcWidth and arcHeight in the rounded rectangle are the width and height of the oval that creates the rounded part of the rectangle.
To draw a rectangle in the background color (clear the area).
g.clearRect(topLeftX,topLeftY,width,height);
To draw a 3-d rectangle (looks like a button)
g.draw3DRect(topLeftX, TopLeftY,width,height,isRaised);
g.fill3DRect(topLeftX,TopLeftY,width,height,isRaised);

17. Drawing on a Blank Picture
Georgia Institute of Technology
Drawing on a Blank Picture
You can make pictures from the “blank” files
They will have all white pixels
640x480.jpg
7inX95in.jpg
You can also create a “blank” picture with a width and height
They will also have all white pixels
Picture blankPicture = new Picture(width,height);

18. Draw a Picture Exercise
Create a method that will draw a simple picture
Use at least one rectangle
Use at least one polygon
Use at least one oval
Use at least one arc
Should this be a class method or object method?
Georgia Institute of Technology

19. Bitmapped Versus Vector Graphics
Georgia Institute of Technology
Bitmapped Versus Vector Graphics
We have been doing bitmapped graphics
Specifying the color of each pixel in the picture
We just wrote a method that drew a simple picture
Which is smaller the program or the picture?
Some applications use vector graphics which are programs that produce the picture
Used in Postscript, Flash, and AutoCAD
Advantages: smaller, easy to change, can be scaled

20. Georgia Institute of Technology
Precision Drawings
How would you draw a stack of filled rectangles starting from the lightest one at the bottom right and the darkest one at the top left.
With 10 pixels between each
Not easy with drawing packages
Georgia Institute of Technology

21. Draw Filled Rectangles Method
Georgia Institute of Technology
Draw Filled Rectangles Method
public void drawFilledRectangles() { Graphics g = this.getGraphics(); Color color = null; // loop 25 times for (int i = 25; i > 0; i--) color = new Color(i * 10, i * 5, i); g.setColor(color); g.fillRect(0,0,i*10,i*10); }
Try drawing a series of filled ovals.

22. 1 // Fig. 28.5: ShowColors.java
2 // Demonstrating Colors
3 import java.awt.*;
4 import javax.swing.*;
5 import java.awt.event.*; 6
7 public class ShowColors extends JFrame {
8 public ShowColors()
9 {
super( "Using colors" ); 11
setSize( 400, 130 );
show();
14 } 15
16 public void paint( Graphics g )
17 {
// set new drawing color using integers
g.setColor( new Color( 255, 0, 0 ) );
g.fillRect( 25, 25, 100, 20 );
g.drawString( "Current RGB: " + g.getColor(), 130, 40 ); 22
// set new drawing color using floats
g.setColor( new Color( 0.0f, 1.0f, 0.0f ) );
g.fillRect( 25, 50, 100, 20 );
g.drawString( "Current RGB: " + g.getColor(), 130, 65 ); 27

23. 28 // set new drawing color using static Color objects
g.setColor( Color.blue );
g.fillRect( 25, 75, 100, 20 );
g.drawString( "Current RGB: " + g.getColor(), 130, 90 ); 32
// display individual RGB values
Color c = Color.magenta;
g.setColor( c );
g.fillRect( 25, 100, 100, 20 );
g.drawString( "RGB values: " + c.getRed() + ", " +
c.getGreen() + ", " + c.getBlue(), 130, 115 );
39 } 40
41 public static void main( String args[] )
42 {
ShowColors app = new ShowColors(); 44
app.addWindowListener(
new WindowAdapter() {
public void windowClosing( WindowEvent e ) {
System.exit( 0 ); } } );
53 }
54 }

24. Graphics 2D

25. Java 2D Graphics – java.awt
Newer drawing classes
More object-oriented
Instead of drawOval() or fillOval() you create a Ellipse2D object and ask a 2d graphics object to draw or fill it
Geometric shapes are in the java.awt.geom package
Advanced Drawing
Support for different types of brushes
Line thickness, dashed lines, etc
Supports cubic curves and general paths
Drawing of gradients and textures
Move, rotate, scale and shear text and graphics
Create composite images
See for the tutorial on 2d graphics from Sun.

26. How To Use Java 2D Cast the Graphics class to Graphics2D
Graphics2D g2 = (Graphics2D) gObj;
Set up the stroke if desired (type of pen)
g2.setStroke(new BasicStroke(widthAsFloat));
Set up any Color, GradientPaint, or TexturePaint
g2.setPaint(Color.blue);
g2.setPaint(blueToPurpleGradient);
g2.setPaint(texture);
Create a geometric shape
Line2D line2D = new Line2D.Double(0.0,0.0,100.0,100.0);
Draw the outline of a geometric shape
g2.draw(line2d);
Fill a geometric shape
g2.fill(rectangle2d);

27. Graphics2D inherits from Graphics
Inherits basic drawing ability from Graphics
Adds more advanced drawing ability
Graphics
Graphics2D
Georgia Institute of Technology

28. Using Graphics2D to Copy an Image
public void copy2D(Picture source, int x, int y) { // get the graphics object Graphics g = this.getGraphics(); Graphics g2 = (Graphics2D) g; // copy the image g2.drawImage(source.getImage(),x,y,null); }
We had created a general copy method that copied a picture to a x and y location in the current picture but we had to copy all the pixels ourselves. But, there is a method that will do this for us in both Graphics and Graphics2D.