Java Image Manipulation Part1

Dream.In.Code> Programming Tutorials> Java TutorialsPage 1 of 1Java Image Manipulation Part 1: Loading Shows how to load

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Dogstopper Posted 18 March 2010 - 08:59 AM

Java Image Manipulation Part 1~ Dogstopper

Image manipulation is something that is very necessaryto do in Java for various reasons, whether that reason beso that you can have images on icons for Jbuttons orJlabels, or have images for games. Either way, they bothstart the same way: you have to load them. Now, I hopethat in today's lesson, I can also demonstrate theimportance of packages when using resources (not solelyfor images). With correct packaging, one does not have toworry about JAR files behaving differently than juststandard class files do.

Loading ImageIconsSo, we shall begin by learning about ImageIcon, which isprimarily for spicing up JLabels, Jbuttons and the like. So,let's begin by loading it:

*Notice the package

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01 package com.thousandcodes.imagespart1;

02

03 import java.net.URL;

04 import javax.swing.*;

05

06 public class Tutorial extends JFrame {

07

08 private JLabel imageLabel;

09 private ImageIcon image;

10

11 public Tutorial() {

12

13 // Get a URL to our image, which is

going to be in a

14 // subdirectory called images.

15 URL imgURL =

getClass().getResource("images/i2.png");

16

17 // If our URL exists

18 if (imgURL != null) {

19 // Then make a new icon. Notice

the second argument

20 // is for those people that are

visually impaired

21 image = new ImageIcon(imgURL,

"This is our icon");

22

23 // Otherwise, if the image cannot be

found, then quit.

24 } else {

25 System.out.println("There was an

error. The image was not loaded");

26 System.exit(1);

27 }

28

29 // Make a JLabel with the image on it

and add it.

30 imageLabel = new JLabel(image);

31 add(imageLabel);

32

Java Image Manipulation Part 1: Loading - Java Tutorials | Dream.In.Code http://www.dreamincode.net/forums/topic/162748-java-image-manipulat...

1 of 7 15/09/2014 01:37 p.m.

Now, the image is called i2.png and is located in thepackage com.thousandcodes.imagespart1.images. Withthis setup, the image can be accessed assuming it is allpackaged together into the same JAR file. The URL isessentially a file location that makes file access easybecause one doesn't have to worry about forward orbackslashes based on the operating system. With a URL,it is always a forward slash.

Then it was a really simple matter of making a new JLabelwith the image, and adding the JLabel to the JFrame.

Loading Images and BufferedImageSo see how easy the loading was with an ImageIcon?Well, that's nice, but not all the time can an ImageIcon beused. Usually, in gaming or image viewing applicationsand such similar things there is a need for something abit...more...Thus comes the abstract class Image andconcrete class BufferedImage. These two classes aregoing to be the focus of later image manipulationtutorials.

Now, loading a BufferedImage is a little bit more tricky asthe loading is not quite so pretty. In this next example, Iwill use an InputStream to load the file. This involvesgrabbing the current class and then loading in the imageas a resource. I understand that this may be complicated,but after working on it for a while, you begin to see it.Now, to actually load the image you can use the read()method of javax.imageio.ImageIO class.

The read() method is static and can take 4 different typesof arguments, a File, an InputSream, anImageInputStream, or a URL. It returns a BufferedImage.For computer-based applications, you will use theInputStream most often and for web-based applications,you will use URL most frequently. Let's take a look at ourpanel.

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33 // Standard JFrame things to do.

34 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

35 pack();

36 setVisible(true);

37 }

38

39 public static void main(String[] args) {

40 new Tutorial();

41 }

42

43 }

01 private class PicturePanel extends JPanel {

02

03 BufferedImage img;

04

05 public PicturePanel() {

06 // Load the image

07 img = getImage("images/space-2.jpg");

08

09 // Make the panel as big as the image

is.

10 this.setPreferredSize(new

Dimension(img.getWidth(), img.getHeight()));

11 }

12

13 public void paintComponent(Graphics g) {

14 // Draw the image on the panel

15 g.drawImage(img, 0,0,null);

16 }

17

18 private BufferedImage getImage(String


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Using ImageIO.read(), this was way easy to load andpaint to a panel. Now all you have to do is make a JFrameclass to use this PicturePanel. Notice thesetPreferredSize(). If you call pack() on a JFrame that hasadded this component, then it will respect the size thatthe JPanel wishes to be at.

Here is the full file including imports so that you can seehow it all works.

filename) {

19 // This time, you can use an

InputStream to load

20 try {

21 // Grab the InputStream for the

image.

22 InputStream in =

getClass().getResourceAsStream(filename);

23

24 // Then read it in.

25 return ImageIO.read(in);

26 } catch (IOException e) {

27 System.out.println("The image was

not loaded.");

28 System.exit(1);

29 }

30 return null;

31 }

32 }

01 package com.thousandcodes.imagespart1;

02

03 import java.awt.Dimension;

04 import java.awt.Graphics;

05 import java.awt.image.BufferedImage;

06 import java.io.IOException;

07 import java.io.InputStream;

08

09 import javax.imageio.ImageIO;

10 import javax.swing.JFrame;

11 import javax.swing.JPanel;

12

13 public class Tutorial extends JFrame {

14

15 public Tutorial() {

16

17 add(new PicturePanel());

18

19 // Standard JFrame things to do.

20 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

21 pack();

22 setVisible(true);

23 }

24

25 private class PicturePanel extends JPanel

{

26


28



31 img = getImage("images/space-

2.jpg");


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Downloading Images Using ImageIORemember how I said that you can use ImageIO to utilizeURLs in web applications? Well, all you have to do is touse the exact same read() method, just with a URL to theInternet image that you wish to download. Let's downloadthe guy from from Java Tutorials located here:http://java.sun.com/...ges/penduke.gif (http://java.sun.com/docs/books/tutorial/images/penduke.gif)

All you have to do is make a quick change to thePicturePanel class. Change the name of the file location inthe constructor and change the InputStream to ajava.net.URL.

32

33 // Make the panel as big as the

image is.



35 }

36

37 public void paintComponent(Graphics g)

{



40 }

41


filename) {


InputStream to load

44 try {

45 // Grab the InputStream for

the image.

46 InputStream in =

getClass().getResourceAsStream(filename);

47


49 return ImageIO.read(in);


51 System.out.println("The image

was not loaded.");

52 System.exit(1);

53 }

54 return null;

55 }

56 }

01 private class PicturePanel extends JPanel {

02


04



07 img = getImage("http://java.sun.com

/docs/books/tutorial/images/penduke.gif

(http://java.sun.com/docs/books/tutorial/images

/penduke.gif) ");

08

09 // Make the panel as big as the

image is.



11 }


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I hope that about covers it! I hope you learned somethingtoday.Oh, and here are the two images that I used if you'reinterested:

i2.png: space-2.jpg:Resized to 50% (was 1000 x 1000) - Click image to enlarge

12

13 public void paintComponent(Graphics g)

{



16 }

17


filename) {


InputStream to load

20 try {

21 // Grab the URL for the image

22 URL url = new URL(filename);

23


25 return ImageIO.read(url);


27 System.out.println("The image

was not loaded.");

28 System.exit(1);

29 }

30 return null;

31 }

32 }


5 of 7 15/09/2014 01:37 p.m.

This post has been edited by Dogstopper: 18 March 2010 - 09:03AM

Replies To: Java Image Manipulation Part 1: Loading

Dogstopper Posted 18 March 2010 - 09:11 AM

Sorry, the font tags messed up coming from the texteditor...I fixed them

NeoTifa Posted 10 August 2010 - 09:30 AM

Beautiful sir.Page 1 of 1

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Java Image Manipulation Part1