Graphics Programming in JAVA : Lab Handout

Computer Graphics (ITEC-613) Java Lab Handout

BS(IT) P-IV First Semester 2016

Lab Handout: 2                 

Graphics Programming in JAVA

By: Dr. Zeeshan Bhatti

Sample Program

import java.awt.Graphics;

import java.awt.Graphics2D;

import java.awt.geom.*;

public class Java2DFrame extends javax.swing.JFrame {

   

    public Java2DFrame() {

        initComponents();

    }

   

    /**

     * This is the method where the graphic objects are drawn.

     *

     */

    public void paint(Graphics g) {

        Graphics2D g2 = (Graphics2D) g;

        Line2D lin = new Line2D.Float(100, 100, 250, 260);

        g2.draw(lin);

       

        g2.draw(new Rectangle2D.Double(10, 50, 100, 100));

                              

         g2.draw(new RoundRectangle2D.Double(200, 200, 100, 100,  50, 50));                     

    }

   

     private void initComponents() {

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        this.setBounds(0,0,400,400);

        this.setLayout(null);

        pack();

    }

   

    /**

     * Starts the program

     *

     */

    public static void main(String args[]) {

                new Java2DFrame().setVisible(true);

    }

}

Drawing Geometric Primitives in JAVA

The Java 2D™ API provides several classes that define common geometric objects such as points, lines, curves, and rectangles. These geometry classes are part of the java.awt.geom package.
The PathIterator interface defines methods for retrieving elements from a path.
The Shape interface provides a set of methods for describing and inspecting geometric path objects. This interface is implemented by the GeneralPath class and other geometry classes.

All examples represented in this section create geometries by using java.awt.geom and then render them by using the Graphics2D class. To begin you obtain a Graphics2D object, for example by casting theGraphics parameter of the paint() method.

public void paint (Graphics g) {

    Graphics2D g2 = (Graphics2D) g;

    ...

}

Point

The Point class creates a point representing a location in (x,y) coordinate space. The subclassesPoint2D.Float and Point2D.Double provide correspondingly float and double precision for storing the coordinates of the point.

//Create Point2D.Double

Point2D.Double point = new Point2D.Double(x, y);

Line

The Line2D class represents a line segment in (x, y) coordinate space. The Line2D.Float andLine2D.Double subclasses specify lines in float and double precision. For example:

// draw Line2D.Double g2.draw(new Line2D.Double(x1, y1, x2, y2));

This class includes several setLine() methods to define the endpoints of the line.
Aternatively, the endpoints of the line could be specified by using the constructor for the Line2D.Float class as follows:

• Line2D.Float(float X1, float Y1, float X2, float Y2)
• Line2D.Float(Point2D p1, Point2D p2)

Use the Stroke object in the Graphics2D class to define the stroke for the line path.

Curves

The java.awt.geom package enables you to create a quadratic or cubic curve segment.

1.   Quadratic Curve Segment

The QuadCurve2D class implements the Shape interface. This class represents a quadratic parametric curve segment in (x, y) coordinate space. The QuadCurve2D.Float and QuadCurve2D.Double subclasses specify a quadratic curve in float and double precision.

// create new QuadCurve2D.Float QuadCurve2D q = new QuadCurve2D.Float(); // draw QuadCurve2D.Float with set coordinates q.setCurve(x1, y1, ctrlx, ctrly, x2, y2); g2.draw(q);

2.   Cubic Curve Segment

The CubicCurve2D class also implements the Shape interface. This class represents a cubic parametric curve segment in (x, y) coordinate space. CubicCurve2D.Float and CubicCurve2D.Double subclasses specify a cubic curve in float and double precision.

// create new CubicCurve2D.Double CubicCurve2D c = new CubicCurve2D.Double(); // draw CubicCurve2D.Double with set coordinates c.setCurve(x1, y1, ctrlx1,                  ctrly1, ctrlx2, ctrly2, x2, y2); g2.draw(c);

 

Rectangle

The Rectangle2D class represents a rectangle defined by a location (x, y) and dimension (w x h). TheRectangle2D.Float and Rectangle2D.Double subclasses specify a rectangle in float and double precision. For example:

// draw Rectangle2D.Double g2.draw(new Rectangle2D.Double(x, y,                                rectwidth,                                rectheight));

The RoundRectangle2D class represents a rectangle with rounded corners defined by a location (x, y), a dimension (w x h), and the width and height of the corner arc. The RoundRectangle2D.Float andRoundRectangle2D.Double subclasses specify a round rectangle in float and double precision.
The rounded rectangle is specified with following parameters:

• Location
• Width
• Height
• Width of the corner arc
• Height of the corner acr

To set the location, size, and arcs of a RoundRectangle2D object, use the method setRoundRect(double a, double y, double w, double h, double arcWidth, double arcHeight). For example:

// draw RoundRectangle2D.Double g2.draw(new RoundRectangle2D.Double(x, y,                                    rectwidth,                                    rectheight,                                    10, 10));

 

Ellipse

The Ellipse2D class represents an ellipse defined by a bounding rectangle. The Ellipse2D.Float andEllipse2D.Double subclasses specify an ellipse in float and double precision.

Ellipse is fully defined by a location, a width and a height. For example:

// draw Ellipse2D.Double g2.draw(new Ellipse2D.Double(x, y,                              rectwidth,                              rectheight));

Arc

To draw a piece of an ellipse, you use the Arc2D class. This class represents an arc defined by a bounding rectangle, a start angle, an angular extent, and a closure type. The Arc2D.Float and Arc2D.Doublesubclasses specify an ellipse in float and double precision.

The Arc2D class defines the following three types of arcs, represented by corresponding constants in this class: OPEN, PIE and CHORD.

Several methods set the size and parameters of the arc:

• Directly, by coordinates
• By supplied Point2D and Dimension2D
• By copying an existing Arc2D

Also, you can use the setArcByCenter method to specify an arc from a center point, given by its coordinates and a radius.

// draw Arc2D.Double g2.draw(new Arc2D.Double(x, y,                          rectwidth,                          rectheight,                          90, 135,                          Arc2D.OPEN));