This is an entry-level article, experts please skip it.
In this article we will learn how to crop an image in Java and save the cropped parts separately to a file.
We will learn through the following steps:
1. Input the image and specify the image path to be processed
2. Allow users to drag and drop the portion to be cropped
3. After selecting, use the Robot class to determine the coordinates of the clipped part.
4. Crop selected image and keep
Next we start the coding part.
Listing1: introduced classes
Copy the code code as follows:
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
illustrate:
1.The Graphics class contains methods for drawing rectangles
2. We use the Rectangle class as the dragged rectangular area for clipping
3.Robot class is used to capture screenshots
4. Use a mouse listener to get the mouse drag time
5. The Robot class uses BufferedImage for image processing
6.File class is used to open image files
7.ImageIO class is used to write images to png or jpg image files
8.JFrame is used to display the interface
Now we write the entry class containing the main method
Listing2: Entry class
Copy the code code as follows:
public class CropImage extends JFrame implements MouseListener, MouseMotionListener
{
int drag_status=0,c1,c2,c3,c4;
public static void main(String args[])
{
new CropImage().start();
}
illustrate:
1.Written a class named CropImage
2. This class extends JFrame to implement all functions of frame
3. Implemented different mouse event listeners to know when the user starts dragging the mouse pointer
4.drag_status variable is used to save the coordinates when the mouse starts dragging
5. We defined the main method to call a start method, which will be defined below
Next is the start method
Listing 2
Copy the code code as follows:
public void start()
{
ImagePanel im=new ImagePanel("F://Wallpaper//wallpapers//1.jpg");
add(im);
setSize(400,400);
setVisible(true);
addMouseListener(this);
addMouseMotionListener( this );
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
illustrate:
1. We define a class called ImagePanel, using the image to be processed as a parameter
2. Place the ImagePanel to display the image in the JFrame and start listening for mouse events.
Next we define methods for handling mouse events
Listing 3: Mouse event handler
Copy the code code as follows:
@Override
public void mouseClicked(MouseEvent arg0) {
}
@Override
public void mouseEntered(MouseEvent arg0) {
}
@Override
public void mouseExited(MouseEvent arg0) {
}
@Override
public void mousePressed(MouseEvent arg0) {
repaint();
c1=arg0.getX();
c2=arg0.getY();
}
@Override
public void mouseReleased(MouseEvent arg0) {
repaint();
if(drag_status==1)
{
c3=arg0.getX();
c4=arg0.getY();
try
{
draggedScreen();
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
@Override
public void mouseDragged(MouseEvent arg0) {
repaint();
drag_status=1;
c3=arg0.getX();
c4=arg0.getY();
}
@Override
public void mouseMoved(MouseEvent arg0) {
}
public void paint(Graphics g)
{
super.paint(g);
int w = c1 - c3;
int h = c2 - c4;
w = w * -1;
h = h * -1;
if(w<0)
w = w * -1;
g.drawRect(c1, c2, w, h);
}
illustrate:
1. When the mouse is pressed, store the current coordinates into c1 and c2
2. Set the drag status variable drag_status to true when the mouse is pressed and dragging begins.
3. When the mouse button is released, it means that the image cropping area has been selected, and the draggedscreen method is called.
4. The paint method is used to display the rectangle when dragging, and draws the rectangle through the current coordinates and the initially recorded coordinates.
Below is the code for the draggedscreen method
Listing 4: draggedScreen method
Copy the code code as follows:
public void draggedScreen()throws Exception
{
int w = c1 - c3;
int h = c2 - c4;
w = w * -1;
h = h * -1;
Robot robot = new Robot();
BufferedImage img = robot.createScreenCapture(new Rectangle(c1, c2,w,h));
File save_path=new File("screen1.jpg");
ImageIO.write(img, "JPG", save_path);
System.out.println("Cropped image saved successfully.");
}}
illustrate:
1. First calculate the height and width of the image
2. Use the Robot class to take a screenshot of the cropped area and save it to another file screen1.jpg
complete code
Listing 5: ImagePanel.java
Copy the code code as follows:
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import javax.swing.ImageIcon;
import javax.swing.JPanel;
class ImagePanel extends JPanel {
private Image img;
public ImagePanel(String img) {
this(new ImageIcon(img).getImage());
}
public ImagePanel(Image img) {
this.img = img;
Dimension size = new Dimension(img.getWidth(null), img.getHeight(null));
// Dimension size = new Dimension(10,10);
setPreferredSize(size);
setMinimumSize(size);
setMaximumSize(size);
setSize(size);
setLayout(null);
}
public void paintComponent(Graphics g) {
g.drawImage(img, 0, 0, null);
}
}
Listing 6:CropImage.java
Copy the code code as follows:
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
public class CropImage extends JFrame implements MouseListener, MouseMotionListener
{
int drag_status=0,c1,c2,c3,c4;
public static void main(String args[])
{
new CropImage().start();
}
public void start()
{
ImagePanel im=new ImagePanel("F://Wallpaper//wallpapers//1.jpg");
add(im);
setSize(400,400);
setVisible(true);
addMouseListener(this);
addMouseMotionListener( this );
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
public void draggedScreen()throws Exception
{
int w = c1 - c3;
int h = c2 - c4;
w = w * -1;
h = h * -1;
Robot robot = new Robot();
BufferedImage img = robot.createScreenCapture(new Rectangle(c1, c2,w,h));
File save_path=new File("screen1.jpg");
ImageIO.write(img, "JPG", save_path);
System.out.println("Cropped image saved successfully.");
}
@Override
public void mouseClicked(MouseEvent arg0) {
}
@Override
public void mouseEntered(MouseEvent arg0) {
}
@Override
public void mouseExited(MouseEvent arg0) {
}
@Override
public void mousePressed(MouseEvent arg0) {
repaint();
c1=arg0.getX();
c2=arg0.getY();
}
@Override
public void mouseReleased(MouseEvent arg0) {
repaint();
if(drag_status==1)
{
c3=arg0.getX();
c4=arg0.getY();
try
{
draggedScreen();
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
@Override
public void mouseDragged(MouseEvent arg0) {
repaint();
drag_status=1;
c3=arg0.getX();
c4=arg0.getY();
}
@Override
public void mouseMoved(MouseEvent arg0) {
}
public void paint(Graphics g)
{
super.paint(g);
int w = c1 - c3;
int h = c2 - c4;
w = w * -1;
h = h * -1;
if(w<0)
w = w * -1;
g.drawRect(c1, c2, w, h);
}
}