Simple Image Viewer in Java

[amhynaya]

Introduction

In this tutorial we will learn how to display picture in Java Application. There is difference between how a picture displayed in application and applet.
For application we require drawImage() method which draws the image to specific component and not the entire frame.
Implementation

Step 1: Creating the components

We require a label, text field where user will enter name or address of the image and a button which when clicked will display the image. A panel to keep all these components.

1. 
   
2. JLabel
   
   label;
   
3. JTextField
   
   name;
   
4. JButton
   
   display;
   
5. 
   
6. JPanel
   
   upperPanel;
   

Step 2:Defining Constructor

In the Constructor of the class, we will create the label , text field and button object and add those object to the Panel. The layout for the main Frame is Border Layout, we will add upperPanel in the NORTH of the frame and other panel for displaying the image in the center of the panel as follows.

1. ImageDisplay(
   
   )
   
2. {
   
3. super
   
   (
   
   "Image Demo"
   
   )
   
   ;
   
4. label=
   
   new
   
   JLabel
   
   (
   
   "Enter name of the Image you want to open"
   
   )
   
   ;
   
5. name=
   
   new
   
   JTextField
   
   (
   
   15
   
   )
   
   ;
   
6. display=
   
   new
   
   JButton
   
   (
   
   "Display Image"
   
   )
   
   ;
   
7. 
   
8. DrawPanel panel=
   
   new
   
   DrawPanel(
   
   )
   
   ;
   
9. display.addActionListener
   
   (
   
   panel)
   
   ;
   
10. upperPanel=
    
    new
    
    JPanel
    
    (
    
    )
    
    ;
    
11. setLayout(
    
    new
    
    BorderLayout
    
    (
    
    )
    
    )
    
    ;
    
12. upperPanel.add
    
    (
    
    label)
    
    ;
    
13. upperPanel.add
    
    (
    
    name)
    
    ;
    
14. upperPanel.add
    
    (
    
    display)
    
    ;
    
15. 
    
16. 
    
17. add(
    
    upperPanel,BorderLayout
    
    .NORTH
    
    )
    
    ;
    
18. add(
    
    panel,BorderLayout
    
    .CENTER
    
    )
    
    ;
    
19. }
    

Step 3: Drawing the Image

For drawing the image, we will create a separate class inside the main class. This class will be a panel and action listener for the button will be in this class.
Data enter by user in the text field is stored in String object and Image is created using that object. Image is created by ImageIcon's getImage() method.

1. public
   
   void
   
   actionPerformed(
   
   ActionEvent
   
   e)
   
2. {
   
3. String
   
   text=
   
   name.getText
   
   (
   
   )
   
   .trim
   
   (
   
   )
   
   ;
   
4. image=
   
   new
   
   ImageIcon
   
   (
   
   text)
   
   .getImage
   
   (
   
   )
   
   ;
   
5. repaint(
   
   )
   
   ;
   
6. 
   
7. }
   

paintComponent() method is used to repaint the panel every time user clicks the display button. For clearing the background, Current color is set as white and then fillRect() method is used to clear the Area. drawImage() method draws the Image from pixel location specified. Image's top left corner will be placed on that pixel location. this keyword specifies that image should be drawn to the same panel.

1. public
   
   void
   
   paintComponent(
   
   Graphics
   
   g)
   
2. {
   
3. setBackground(
   
   Color
   
   .WHITE
   
   )
   
   ;
   
4. g.setColor
   
   (
   
   Color
   
   .WHITE
   
   )
   
   ;
   
5. g.fillRect
   
   (
   
   10
   
   ,10
   
   ,800
   
   ,600
   
   )
   
   ;
   
6. g.drawImage
   
   (
   
   image,10
   
   ,10
   
   ,this
   
   )
   
   ;
   
7. }
   

Step 4: Defining main() method

main() method is defined which set the different properties of the frame and execution begins from here.

1. public
   
   static
   
   void
   
   main(
   
   String
   
   [
   
   ]
   
   args)
   
   {
   
2. 
   
3. 
   
4. ImageDisplay img=
   
   new
   
   ImageDisplay(
   
   )
   
   ;
   
5. img.setSize
   
   (
   
   800
   
   ,600
   
   )
   
   ;
   
6. img.setVisible
   
   (
   
   true
   
   )
   
   ;
   
7. img.setDefaultCloseOperation
   
   (
   
   EXIT_ON_CLOSE)
   
   ;
   
8. img.setResizable
   
   (
   
   false
   
   )
   
   ;
   
9. }
   

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