Develop Reference

How do I set a well functioning JFrame to be inside another JFrame as a internal JFrame?

Now I know how JInternalFrame works but what I am trying to do is give an already well-functioning JFrame with a space in a place where I have placed an empty Internal Frame.
I want it to grab what I have in the already existing JFrame in the package and place it in that Internal JFrame. Here is the JFrame I want to be placed into another JFrame as an internal frame.
Why I wanna do it this way because the inner frame has a lot of functionality and the container Jframe would be too big to do it all in itself.
What it does is not much of an interest to the thing I wanna do but here it is: It takes images and makes them pure b/w and takes 2 clicks on the screen and stores every pixel between them in a 2d array with their coordinates.
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
public class imageFilt {
public static void main(String[] args) {new imageFilt();}
//--basic initialization
int[] x= new int[3], y= new int[3];
static int[] black= new int[3]; //---------------- if black is 0, then the pixel is black
int clr;int flag=0;
//-----------------------------initialize the screen as runnable. dont disturb the fit
public imageFilt() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());} catch (Exception ex) {}
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private BufferedImage master;
private BufferedImage blackWhite;
public TestPane() {
//----------------------try/catch for (pure black || pure white)
try {
master = ImageIO.read(new File("D:\\colz\\java\\1Aakansh thapa\\1_1_2.jpg"));
blackWhite = new BufferedImage(master.getWidth(), master.getHeight(), BufferedImage.TYPE_BYTE_BINARY);
Graphics2D g2d = blackWhite.createGraphics();
g2d.drawImage(master, 0, 0, this);
g2d.dispose();
}catch (IOException ex) {ex.printStackTrace();}
//--------------------------1st and 2nd click point data and color
this.addMouseListener(new MouseListener() {
int[] isFristEmpty;
#Override
public void mouseClicked(MouseEvent e1) {
int[] temp =new int[3]; //external container so i can get 1st and 2nd separately
temp[0] = (int) e1.getX();
temp[1] = (int) e1.getY();
clr = blackWhite.getRGB(temp[0], temp[1]);
temp[2] = (clr & 0x00ff0000) >> 16;//--------------------bit map to find if red is there or not.
//-------------------------------------------------------since its pure b/w, if red 0, its white.
if(isFristEmpty==null) {
isFristEmpty=temp;
x[0] = temp[0]; y[0] = temp[1]; black[0]=temp[2];//------1st click
}else {
x[1] = temp[0]; y[1] = temp[1]; black[1]=temp[2];//-----2nd click
isFristEmpty=null; //so the 3rd click is considered 1st click again
flag=1;
}
if (flag==1) {
System.out.print("X1: "+x[0]+" & "+"Y1: "+y[0]+" "+"(225 if white): "+black[0]+"\t");
System.out.println("X2: "+x[1]+" & "+"Y2: "+y[1]+" "+"(225 if white): "+black[1]);
counter(x,y);
}
}
#Override public void mousePressed(MouseEvent e) {}
#Override public void mouseReleased(MouseEvent e) {}
#Override public void mouseEntered(MouseEvent e) {}
#Override public void mouseExited(MouseEvent e) {}
});
}
//--------------------------------------------DDA block
private void counter(int x[],int y[]) {
if(flag!=1) return;//-------------------to only go to counter method after it takes that 2nd click
int dx = (x[1] - x[0]);
int dy = (y[1] - y[0]);//--------------makes it applicable for both inclinations (we do not have math.abs implies-> -ve goes as -ve)
int step = Math.abs(dx) > Math.abs(dy) ? Math.abs(dx) : Math.abs(dy);
System.out.println("Steps: "+step);
float Xinc = dx / (float) step;
float Yinc = dy / (float) step;
int[][] tog= new int[step][3];
tog[0][0]=x[0]; tog[0][1]=y[0];
//---------------------------------------------------------------send value of x1 and y1 to listOfCoordinates
float xt=x[0],yt=y[0]; int i=0, j=1; int a=0 ,b=0;
while (a!=x[1] && b!=y[1]){
xt += Xinc;
yt += Yinc;
a=(int) xt; b=(int) yt;
tog[j][i] = a;
tog[j][i+1] = b;
//System.out.println(tog[j][i]+" "+tog[j][i+1]); //*------------to print all that is saved
if(i==1) i=0;
}
}
//------------image size and such stuff. don't touch it
#Override
public Dimension getPreferredSize() {
Dimension size = super.getPreferredSize();
if (master != null) {
size = new Dimension(master.getWidth(), master.getHeight());
}
return size;
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (master != null) {
int x = (getWidth() - (master.getWidth())) / 2;
int y = (getHeight() - master.getHeight()) / 2;
g.drawImage(blackWhite, x, y, this);
}
}
}
}
Hope what I wanna do makes sense.

Just imported the frame that I want into the JFrame I want it to be in and did this.
JInternalFrame printImg = new JInternalFrame(inTitle);
JPanel inLabel= new JPanel();
inLabel.add(new TestPane());
printImg.add(inLabel);
printImg.setVisible(true);
just for people who want to know when they stumble upon the post. Wouldnt want them to stay unanswered.
might also work if u copy-paste the Testpane (as the example) part and do the same thing for the rest instead of importing.

PaintComponent is not being called-Java

My code is supposed to draw a random sized image three times in random locations. For some reason, when I run this code using BlueJ, all that shows up is a gray screen. I think it is because PaintComponent isn't being called, but I am not quite sure. What went wrong with my code and how can I fix it?
class PanelHolder extends JPanel{//class PanelHolder extends JPanel
//variables
public boolean threesharks;
public int xcoord;
public int ycoord;
public int ratio;
public Image i;
public int w;
public int h;
public boolean background=true;
Color water = new Color(136, 180, 231);
public PanelHolder(){//constructor
i = Toolkit.getDefaultToolkit().getImage("$harkz.png");
}
public void randomxy(){
for(int x=0;x<3;x++){
threesharks=true;
ycoord=(int)(Math.random()*300+200);//use math.random to figure out coordinates and sizing
xcoord=(int)(Math.random()*1000+0);//make a loop
ratio=(int)(Math.random()*5+1);
w=ratio*523;
h=ratio*195;
repaint();
System.out.println("I'm in randomxy");
//call repaint() each time
//after three times, make threesharks=false
}
threesharks=false;
}
public void paintComponent(Graphics g){
if(threesharks){
setBackground(water);
System.out.print("hi!");
if(background){
super.paintComponent(g);//set backgroun
background=false;
}
g.drawImage(i, xcoord, ycoord, w, h, this);
}
}
}

You seem to have a misunderstanding with how painting works in Swing. Swing will call your paintComponent when ever it thinks your component needs to be repainted, this might occur for many different reasons, many of which you don't have control over.
Painting in Swing is destructive, that is, each time your paintComponent method is called, you are expected to repaint the entire state of the component from scratch, painting is not accumalitive.
This means that you need to store the state of things you want to paint in some meaningful manner and re-use these values are needed.
Have a look at Painting in AWT and Swing and Performing Custom Painting for more details about how painting works in Swing
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new PanelHolder());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
class PanelHolder extends JPanel {//class PanelHolder extends JPanel
//variables
public boolean threesharks;
public BufferedImage i;
public boolean background = true;
Color water = new Color(136, 180, 231);
private Point[] points;
private Image[] images;
public PanelHolder() {
//constructor
try {
i = ImageIO.read(...);
} catch (IOException ex) {
ex.printStackTrace();
}
randomxy();
}
#Override
public Dimension getPreferredSize() {
return new Dimension(800, 800);
}
public void randomxy() {
points = new Point[3];
images = new Image[3];
for (int x = 0; x < 3; x++) {
points[x] = new Point();
double ratio = (Math.random() * 6d) + 0.1d;
int width = (int) (ratio * i.getWidth());
int height = (int) (ratio * i.getHeight());
points[x].y = Math.max(0, (int) (Math.random() * 800) - height);//use math.random to figure out coordinates and sizing
points[x].x = Math.max(0, (int) (Math.random() * 800) - width);//make a loop
images[x] = i.getScaledInstance(width, height, Image.SCALE_SMOOTH);
}
}
public void paintComponent(Graphics g) {
super.paintComponent(g);//set backgroun
g.setColor(water);
g.fillRect(0, 0, getWidth(), getHeight());
if (points != null && images != null) {
for (int index = 0; index < points.length; index++) {
g.drawImage(images[index], points[index].x, points[index].y, this);
}
}
}
}
}
This is a rough example, which uses Image#getScaledInstance which is not generally recommended, but works for the example.
Have a look at The Perils of Image.getScaledInstance() for more details
Have a look at Quality of Image after resize very low -- Java and Java: maintaining aspect ratio of JPanel background image for possible (scaling) alternatives
I'd also have a look at Reading/Loading an Image for a better mechanism for loading images

How do I fire a custom event when a new Rectangle is drawn?

I created a graphical component that allows you to view an image and allows you to make a selection of a part of the image: the selection of a portion of the image is accomplished by drawing a rectangle on this image (using drag-and-drop).
To this purpose, I used this example, which created a subclass of JLabel in order to draw the image and in order to deal with the drawing of the rectangle. Then I put an instance of this subclass within a JPanel, in order to have the image always positioned at the center of the panel.
FigurePanel.java
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridBagLayout;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import javax.swing.ImageIcon;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.event.MouseInputAdapter;
public class FigurePanel extends JPanel
{
private SelectionLabel imageLabel = null;
public FigurePanel()
{
this.setLayout(new GridBagLayout());
imageLabel = new SelectionLabel();
this.add(imageLabel, null);
}
public void setImage(Image image)
{
imageLabel.setImage(image);
}
private class SelectionLabel extends JLabel
{
private Rectangle currentRect = null;
private Rectangle rectToDraw = null;
private final Rectangle previousRectDrawn = new Rectangle();
public SelectionLabel()
{
super();
setOpaque(true);
SelectionListener listener = new SelectionListener();
addMouseListener(listener);
addMouseMotionListener(listener);
}
public void setImage(Image image)
{
currentRect = null;
rectToDraw = null;
previousRectDrawn.setBounds(0, 0, 0, 0);
setIcon(new ImageIcon(image));
}
private class SelectionListener extends MouseInputAdapter
{
#Override
public void mousePressed(MouseEvent e)
{
int x = e.getX();
int y = e.getY();
currentRect = new Rectangle(x, y, 0, 0);
updateDrawableRect(getWidth(), getHeight());
repaint();
}
#Override
public void mouseDragged(MouseEvent e)
{
updateSize(e);
}
#Override
public void mouseReleased(MouseEvent e)
{
updateSize(e);
}
/*
* Update the size of the current rectangle
* and call repaint. Because currentRect
* always has the same origin, translate it
* if the width or height is negative.
*
* For efficiency (though
* that isn't an issue for this program),
* specify the painting region using arguments
* to the repaint() call.
*
*/
void updateSize(MouseEvent e)
{
int x = e.getX();
int y = e.getY();
currentRect.setSize(x - currentRect.x,
y - currentRect.y);
updateDrawableRect(getWidth(), getHeight());
Rectangle totalRepaint = rectToDraw.union(previousRectDrawn);
repaint(totalRepaint.x, totalRepaint.y,
totalRepaint.width, totalRepaint.height);
}
}
#Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g); //paints the background and image
//If currentRect exists, paint a box on top.
if (currentRect != null) {
//Draw a rectangle on top of the image.
g.setXORMode(Color.white); //Color of line varies
//depending on image colors
g.drawRect(rectToDraw.x, rectToDraw.y,
rectToDraw.width - 1, rectToDraw.height - 1);
System.out.println("rectToDraw: " + rectToDraw);
}
}
private void updateDrawableRect(int compWidth, int compHeight)
{
int x = currentRect.x;
int y = currentRect.y;
int width = currentRect.width;
int height = currentRect.height;
//Make the width and height positive, if necessary.
if (width < 0) {
width = 0 - width;
x = x - width + 1;
if (x < 0) {
width += x;
x = 0;
}
}
if (height < 0) {
height = 0 - height;
y = y - height + 1;
if (y < 0) {
height += y;
y = 0;
}
}
//The rectangle shouldn't extend past the drawing area.
if ((x + width) > compWidth) {
width = compWidth - x;
}
if ((y + height) > compHeight) {
height = compHeight - y;
}
//Update rectToDraw after saving old value.
if (rectToDraw != null) {
previousRectDrawn.setBounds(
rectToDraw.x, rectToDraw.y,
rectToDraw.width, rectToDraw.height);
rectToDraw.setBounds(x, y, width, height);
} else {
rectToDraw = new Rectangle(x, y, width, height);
}
}
}
}
FigurePanelTest.java
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Image;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
public class FigurePanelTest extends JFrame
{
public FigurePanelTest()
{
FigurePanel imagePanel = new FigurePanel();
JScrollPane imageScrollPane = new JScrollPane();
imageScrollPane.setPreferredSize(new Dimension(420, 250));
imageScrollPane.setViewportView(imagePanel);
JButton imageButton = new JButton("Load Image");
imageButton.addActionListener(
new ActionListener()
{
#Override
public void actionPerformed(ActionEvent evt)
{
JFileChooser fc = new JFileChooser();
int returnValue = fc.showOpenDialog(null);
if (returnValue == JFileChooser.APPROVE_OPTION) {
File selectedFile = fc.getSelectedFile();
System.out.println(selectedFile.getName());
try
{
Image image = ImageIO.read(selectedFile.getAbsoluteFile());
imagePanel.setImage(image);
imageScrollPane.getViewport().setViewPosition(new Point(0, 0));
}
catch(IOException e)
{
e.printStackTrace();
}
}
}
}
);
Container container = getContentPane();
container.setLayout(new BorderLayout());
container.add(imageScrollPane, BorderLayout.CENTER);
container.add(imageButton, BorderLayout.NORTH);
setSize(600, 400);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
/**
* #param args the command line arguments
*/
public static void main(String args[]) {
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new FigurePanelTest().setVisible(true);
}
});
}
}
The private class SelectionLabel is the class SelectionArea from this example.
When a new rectangle is drawn, a message is printed on the console. Now I would replace the printing of the message with the firing of a custom event, so that the position and size of the rectangle are accessible to the application business logic.
I read how to create a custom event in Java. Moreover, this article identifies two super types for creating events: EventObject and AWTEvent. This articles states:
Normally you extend AWTEvent for events generated by a graphical
component and EventObject any other time.
Since the event concerning the selection of a part of the image is generated by a graphical component (that is the FigurePanel panel), I could implement the ImageSelectionEvent class by extending AWTEvent, as the following code snippet.
public class ImageSelectionEvent extends AWTEvent
{
public ImageSelectionEvent(Object source, int id) {
super(source, id);
}
}
The documentation identifies the id as the event type. So, what value should be assigned to this parameter?
Moreover, why does the constructor of EventObject class be devoid of the id parameter?
When creating an event class, you must guarantee that the event is
immutable. The event generator will share the same event instance
among the listeners; so ensure any one listener cannot change the
event's state.
What about this?

I don't know what is needed to create a custom event.
However, since you are extending JLabel maybe you can just create a PropertyChangeEvent.
To generated the event you would just use something like:
firePropertyChange("selectionRectangle", oldRectangle, newRectangle);
Then you can use a PropertyChangeListener to listen for "selectionRectangle" changes.

The Javadoc for AWTEvent says:
Subclasses of this root AWTEvent class defined outside of the java.awt.event package should define event ID values greater than the value defined by RESERVED_ID_MAX.
This value is 1999. You can set it to whatever you want that's higher than that. This value is specified by all the different types of Swing events, and Swing uses values that are less than that. For example, the MouseEvent event types use values from 500-507.
The main thing is to use a consistent value for your events.
Finally, I would consider subclassing ComponentEvent over AWTEvent as the source of your event is a Component, not an Object.

Swing Graphics object not drawing over image in JLabel

I am creating a Java program that receives and plots GPS coordinates over a TCP socket connection on a 2D image of a map. The constructor creates the JFrame and graphical components and then starts off a SwingWorker thread to handle getting coordinates from the socket and then drawing an oval to represent the fix on the map.
I am able to always receive data over the connection but the program does not reliably draw points over the image.
Any suggestions and thank you!
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.io.File;
import java.util.List;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingWorker;
import connectivity.TelitSocketServer;
import calculations.PlottingMath;
import objects.ElephantFix;
#SuppressWarnings("serial")
public class Gui
{
protected JFrame mainWindow;
protected JPanel mapArea = new JPanel();
private ReceiveFix rfix;
public Gui()
{
// TODO Auto-generated constructor stub
mainWindow = new JFrame();
// Load map image
Image map = null;
try
{
File mapImage = new File("map_images/AWE_PLOT.JPG");
map = ImageIO.read(mapImage);
} catch (Exception e)
{
System.out.println(e.toString());
}
JLabel label = new JLabel(new ImageIcon(map));
mapArea.add(label);
// Map Image Dimensions
mainWindow.getContentPane().add(mapArea, "Center");
mainWindow.setSize(471, 670);
mainWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
mainWindow.setTitle("ElePlotter");
mainWindow.setVisible(true);
rfix = new ReceiveFix();
rfix.execute();
}
public static void main(String args[])
{
new Gui();
}
private class ReceiveFix extends SwingWorker<Void, ElephantFix>
{
#Override
protected Void doInBackground()
{
// Start the server
String fix = "";
TelitSocketServer currentConnection = new TelitSocketServer();
try
{
// Wait for client to connect
currentConnection.intializeConnection();
while (true)
{
// Parse and convert received GPS fix into arc radians
fix = currentConnection.readLine();
String[] split = fix.split(" ");
double latWholeDegrees = Double.parseDouble(split[0]
.substring(0, 3));
double longWholeDegrees = Double.parseDouble(split[1]
.substring(0, 3));
double latMinutes = Double.parseDouble(split[0]
.substring(3)) * .166667;
double longMinutes = Double.parseDouble(split[1]
.substring(3)) * .166667;
double lat = latWholeDegrees - latMinutes / 10;
double lon = longWholeDegrees + longMinutes / 10;
publish(new ElephantFix(lat, lon));
}
} catch (Exception e)
{
e.printStackTrace();
}
// Return null if somehow unable to publish node data
return null;
}
#Override
protected void process(List<ElephantFix> fixes)
{
int x, y;
// Get the most recently published node
ElephantFix aFix = fixes.get(fixes.size() - 1);
// Translate lat/long into map X/Y pixel
x = PlottingMath.getCurrentPixelX(aFix.getLatitude(),
aFix.getLongitude());
y = PlottingMath.getCurrentPixelY(aFix.getLatitude(),
aFix.getLongitude());
// Plot on image
Graphics g = mapArea.getGraphics();
g.setColor(Color.RED);
g.fillOval(x, y, 15, 15);
// mapArea.validate();
//
// mapArea.repaint();
//
// Gui.this.repaint();
}
}
}

mapArea.getGraphics(); is not how custom painting in Swing is done.
Start by taking a look at Performing Custom Painting for more details.
Adding a component to a container ensures that the child component will always be painted over the container...
JLabel label = new JLabel(new ImageIcon(map));
mapArea.add(label);
You have that backwards. It might be better to add both the label and mapArea to the same container
The next problem you will need to overcome is the fact that you will need to get your painting component to reside over the top of your label.
To this end you could...
Use a glass pane
Use a OverlayLayout
Use a GridBagLayout
Update with example
There are any number of ways to achieve this, you could use multiple components which act as layers onto which you could add other components or perform custom painting.
This is not as easy it as it sounds. Most layout managers don't consider two components sharing the same space. You also have to manage the connection between the layers, so if the map is centered within the lowest layer, but the available space is larger or smaller than the map, offsets begin to drift...messy...
A simpler solution would be to use a single component and render all the content onto it, for example...
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class TestMap {
public static void main(String[] args) {
new TestMap();
}
public TestMap() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
MapPane pane = new MapPane();
pane.dropPinAt(174, 147);
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(pane);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class MapPane extends JPanel {
private BufferedImage img;
private BufferedImage pin;
private List<Point> pins;
public MapPane() {
pins = new ArrayList<>(25);
try {
img = ImageIO.read(getClass().getResource("/Map.jpg"));
pin = ImageIO.read(getClass().getResource("/Pin.png"));
} catch (IOException ex) {
ex.printStackTrace();
}
}
#Override
public Dimension getPreferredSize() {
return img == null ? new Dimension(200, 200) : new Dimension(img.getWidth(), img.getHeight());
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (img != null) {
Graphics2D g2d = (Graphics2D) g.create();
int x = (getWidth() - img.getWidth()) / 2;
int y = (getHeight() - img.getHeight()) / 2;
g2d.drawImage(img, x, y, this);
for (Point p : pins) {
// Offset the pin x/y
// to allow the point to land on the desired location
p.x -= 6;
p.y -= 64;
System.out.println(p);
g2d.drawImage(pin, p.x, p.y, this);
}
g2d.dispose();
}
}
protected void dropPinAt(int x, int y) {
pins.add(new Point(x, y));
}
}
}

You should not be drawing with a Graphics object obtained by calling getGraphics() on a Component. Doing this will give you a Graphics object that doesn't persist and an image that doesn't persist. Instead either draw on a BufferedImage with its Graphics object and display it in the GUI, or iterate through the data collection in the JPanel's paintComponent method and draw with the data obtained.

How to efficiently draw a subpart of an image in Swing

Let's say I have a BufferedImage of type TYPE_4BYTE_ABGR in Swing and I want to draw only a part of it. For example I would like to draw the left half only or some triangular shape or something more complicated.
Reason is that the final image shall be composed from subparts of individual images I have.
What's the best way to do that?
I would prefer to define a polygon and then use this shape as a mask for drawing, if this is possible.
My current idea: make a copy of the individual image and set all pixels outside the wished shape to transparent, then draw the whole image. I think this might work but might be too slow with the copying and all.
edit:
I tested the solution of Guillaume and found that it works and does not extremely slow down the painting. Using a clip resulted in an increase of drawing time from 14ms to 35ms but these times are very inaccurate. I used profiling the EDT from here. Here is the code.
import java.awt.AWTEvent;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
/**
*
*/
public class ClipTilesTest {
// tile size and number of tiles in each row/column
private static int TILE_SIZE = 100;
private static int TILE_NUM = 6;
// taken from https://stackoverflow.com/questions/5541493/how-do-i-profile-the-edt-in-java-swing
public static class TimedEventQueue extends EventQueue {
#Override
protected void dispatchEvent(AWTEvent event) {
long startNano = System.nanoTime();
super.dispatchEvent(event);
long endNano = System.nanoTime();
if (endNano - startNano > 5000000) {
System.out.println(((endNano - startNano) / 1000000) + "ms : " + event);
}
}
}
private static void initUI() {
Toolkit.getDefaultToolkit().getSystemEventQueue().push(new TimedEventQueue());
// download image
BufferedImage image;
try {
image = ImageIO.read(new URL("http://download.chip.eu//ii/163859211_4b28e1e687.jpg"));
} catch (IOException ex) {
ex.printStackTrace();
return;
}
// take out small chunk
final BufferedImage tile = image.getSubimage(0, 0, TILE_SIZE, TILE_SIZE);
JFrame frame = new JFrame();
frame.setTitle(ClipTilesTest.class.getSimpleName());
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
// the panel containing some tiles
JPanel view = new JPanel() {
#Override
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D) g;
for (int i = 0; i < TILE_NUM; i++) {
for (int j = 0; j < TILE_NUM; j++) {
// version 1
/*
g2d.setClip(i * TILE_SIZE, j * TILE_SIZE , (i+1)*TILE_SIZE, (j+1)*TILE_SIZE);
g2d.drawImage(tile, i * TILE_SIZE, j * TILE_SIZE, null);
*/
// version 2
g2d.setClip(i * TILE_SIZE, j * TILE_SIZE , i*TILE_SIZE + TILE_SIZE/2, (j+1)*TILE_SIZE);
g2d.drawImage(tile, i * TILE_SIZE, j * TILE_SIZE, null);
g2d.setClip(i * TILE_SIZE + TILE_SIZE/2, j * TILE_SIZE , (i+1)*TILE_SIZE , (j+1)*TILE_SIZE);
g2d.drawImage(tile, i * TILE_SIZE, j * TILE_SIZE, null);
}
}
}
};
view.setPreferredSize(new Dimension(TILE_SIZE * TILE_NUM, TILE_SIZE * TILE_NUM));
// add, pack, set visible
frame.add(view);
frame.pack();
frame.setVisible(true);
// now make a repaint event, so we can start measuring
view.repaint();
}
/**
* #param args the command line arguments
*/
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
ClipTilesTest.initUI();
}
});
}
}

One easy way to achieve this effect, is to modify the "clip" of the Graphics object and to set it to the shape you want to draw.
I don't know how efficient this is, but you could consider caching the clipped image and then draw the entire cached image.
Here is a small demo code:
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.Shape;
import java.awt.geom.Ellipse2D;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class TestClippedPanel {
private static class ClippedPanel extends JPanel {
private ImageIcon image;
private List<Shape> shapes;
public ClippedPanel() throws MalformedURLException {
shapes = new ArrayList<Shape>();
image = new ImageIcon(new URL("http://download.chip.eu//ii/163859211_4b28e1e687.jpg"));
Random random = new Random();
for (int i = 0; i < 10; i++) {
int x = random.nextInt(image.getIconWidth() - 1);
int y = random.nextInt(image.getIconHeight() - 1);
int w = random.nextInt(image.getIconWidth() - x) + 1;
int h = random.nextInt(image.getIconHeight() - y) + 1;
shapes.add(new Rectangle(x, y, w, h));
}
for (int i = 0; i < 10; i++) {
int x = random.nextInt(image.getIconWidth() - 1);
int y = random.nextInt(image.getIconHeight() - 1);
int w = random.nextInt(image.getIconWidth() - x) + 1;
int h = random.nextInt(image.getIconHeight() - y) + 1;
shapes.add(new Ellipse2D.Double(x, y, w, h));
}
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Image img = image.getImage();
for (Shape shape : shapes) {
((Graphics2D) g).setClip(shape);
g.drawImage(img, 0, 0, this);
}
}
#Override
public Dimension getPreferredSize() {
return new Dimension(image.getIconWidth(), image.getIconHeight());
}
}
protected void initUI() throws MalformedURLException {
final JFrame frame = new JFrame(TestClippedPanel.class.getSimpleName());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final ClippedPanel panel = new ClippedPanel();
frame.add(panel);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
try {
new TestClippedPanel().initUI();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
}
}