2D Graphics in Java

Introduction#

Graphics are visual images or designs on some surface, such as a wall, canvas, screen, paper, or stone to inform, illustrate, or entertain. It includes: pictorial representation of data, as in computer-aided design and manufacture, in typesetting and the graphic arts, and in educational and recreational software. Images that are generated by a computer are called computer graphics.

The Java 2D API is powerful and complex. There are multiple ways to do 2D graphics in Java.

Example 1: Draw and Fill a Rectangle Using Java

This is an Example which print rectangle and fill color in the rectangle. https://i.stack.imgur.com/dlC5v.jpg

Most methods of the Graphics class can be divided into two basic groups:

1. Draw and fill methods, enabling you to render basic shapes, text, and images
2. Attributes setting methods, which affect how that drawing and filling appears

Code Example: Let us start this with a little example of drawing a rectangle and filling color in it. There we declare two classes, one class is MyPanel and other Class is Test. In class MyPanel we use drawRect( ) & fillRect( ) mathods to draw rectangle and fill Color in it. We set the color by setColor(Color.blue) method. In Second Class we Test our graphic which is Test Class we make a Frame and put MyPanel with p=new MyPanel() object in it.By running Test Class we see a Rectangle and a Blue Color Filled Rectangle.

First Class: MyPanel

import javax.swing.*;
import java.awt.*;
// MyPanel extends JPanel, which will eventually be placed in a JFrame
public class MyPanel extends JPanel { 
    // custom painting is performed by the paintComponent method
    @Override
    public void paintComponent(Graphics g){
        // clear the previous painting
        super.paintComponent(g);
        // cast Graphics to Graphics2D
        Graphics2D g2 = (Graphics2D) g;
        g2.setColor(Color.red); // sets Graphics2D color
        // draw the rectangle
        g2.drawRect(0,0,100,100); // drawRect(x-position, y-position, width, height)
        g2.setColor(Color.blue);
        g2.fillRect(200,0,100,100); // fill new rectangle with color blue
    } 
}

Second Class: Test

import javax.swing.;
import java.awt.;    
public class Test { //the Class by which we display our rectangle    
    JFrame f;    
    MyPanel p;    
    public Test(){    
        f = new JFrame();    
        // get the content area of Panel.    
        Container c = f.getContentPane();    
        // set the LayoutManager
        c.setLayout(new BorderLayout());        
        p = new MyPanel();    
        // add MyPanel object into container    
        c.add(p); 
        // set the size of the JFrame
        f.setSize(400,400);    
        // make the JFrame visible
        f.setVisible(true);    
        // sets close behavior; EXIT_ON_CLOSE invokes System.exit(0) on closing the JFrame
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);    
    }       
    
    public static void main(String args[ ]){    
        Test t = new Test();     
    } 
}

For More Explanation about Border Layout: https://docs.oracle.com/javase/tutorial/uiswing/layout/border.html

paintComponent( )
• It is a main method for painting
• By default, it first paints the background
• After that, it performs custom painting (drawing circle, rectangles etc.)

Graphic2D refers Graphic2D Class

Note: The Java 2D API enables you to easily perform the following tasks:

• Draw lines, rectangles and any other geometric shape.
• Fill those shapes with solid colors or gradients and textures.
• Draw text with options for fine control over the font and rendering process.
• Draw images, optionally applying filtering operations.
• Apply operations such as compositing and transforming during any of the above rendering operations.

Example 2: Drawing and Filling Oval

import javax.swing.*;    
import java.awt.*;    

public class MyPanel extends JPanel {
    @Override
    public void paintComponent(Graphics g){    
        // clear the previous painting
        super.paintComponent(g);    
        Graphics2D g2 = (Graphics2D)g;    
        g2.setColor(Color.blue);    
        g2.drawOval(0, 0, 20,20);  
        g2.fillOval(50,50,20,20);    
    }
}

g2.drawOval(int x,int y,int height, int width);
This method will draw an oval at specified x and y position with given height and width. 

g2.fillOval(int x,int y,int height, int width); This method will fill an oval at specified x and y position with given height and width.