CODEWITHSUNDEEP
javaswingpngimage
itro
itro

Reputation: 7228

why picture doesn't show up in swing in java?

I want to show images in a Border-layout panel in center. I create image panel as below and then add it to the center of Border-layout. I don't know why image doesn't show up and there is no error too. What can be the reason and how can i fix it?

public class ImagePanel extends WebPanel {
private Image image;
private Image scaledImage;
private int imageWidth = 0;
private int imageHeight = 0;
//constructor
public ImagePanel() {
    super();
}
public void loadImage(String file) throws IOException {
    File filetest= new File("C:\\tmp\\axiuser\\Pictures\\CLA0014.png");
    image = ImageIO.read(filetest);//new File(file)
    imageWidth = image.getWidth(this);
    imageHeight = image.getHeight(this);
    setScaledImage();
}
//e.g., containing frame might call this from formComponentResized
public void scaleImage() {
    setScaledImage();
}
//override paintComponent
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    if ( scaledImage != null ) {
        //System.out.println("ImagePanel paintComponent " + ++paintCount);
        g.drawImage(scaledImage, 0, 0, this);
    }
}
private void setScaledImage() {
    if ( image != null ) {
        //use floats so division below won't round
        float iw = imageWidth;
        float ih = imageHeight;
        float pw = this.getWidth();   //panel width
        float ph = this.getHeight();  //panel height
        if ( pw < iw || ph < ih ) {
            if ( (pw / ph) > (iw / ih) ) {
                iw = -1;
                ih = ph;
            } else {
                iw = pw;
                ih = -1;
            }
            //prevent errors if panel is 0 wide or high
            if (iw == 0) {
                iw = -1;
            }
            if (ih == 0) {
                ih = -1;
            }
            scaledImage = image.getScaledInstance(
                        new Float(iw).intValue(), new Float(ih).intValue(), Image.SCALE_DEFAULT);
        } else {
            scaledImage = image;
        }
    }
}

}

Upvotes: 3

Views: 1286

Answers (6)

user unknown
user unknown

Reputation: 36229

You never call your method 

public void loadImage (String file)

SSCCE:

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.io.*;
import javax.imageio.*;

public class ImagePanel extends JPanel {
    private Image image;
    private Image scaledImage;

    public void loadImage (String filename) throws IOException {
        image = ImageIO.read (new File (filename)); 
        setScaledImage ();
    }

    public void paintComponent (Graphics g) {
        super.paintComponent (g);
        if ( scaledImage != null) {
            // System.out.println ("ImagePanel paintComponent ");
            g.drawImage (scaledImage, 0, 0, this);
        }
    } 

    private void setScaledImage () {
        if (image != null) {
            //use floats so division below won't round
            int imageWidth = image.getWidth (this);
            int imageHeight = image.getHeight (this);
            float iw = imageWidth;
            float ih = imageHeight;
            float pw = this.getWidth ();   //panel width
            float ph = this.getHeight ();  //panel height
            if ( pw < iw || ph < ih) {
                if ( (pw / ph) > (iw / ih)) {
                    iw = -1;
                    ih = ph;
                } else {
                    iw = pw;
                    ih = -1;
                }
                //prevent errors if panel is 0 wide or high
                if (iw == 0) {
                    iw = -1;
                }
                if (ih == 0) {
                    ih = -1;
                }
                scaledImage = image.getScaledInstance (
                new Float (iw).intValue (), new Float (ih).intValue (), Image.SCALE_DEFAULT);
            } else {
                scaledImage = image;
            }
        }
    }   

    public static void main (String [] args) throws IOException {
        ImagePanel ip = new ImagePanel ();
        ip.loadImage ("./sample.png");
        JFrame jf = new JFrame ();
        jf.setLayout (new BorderLayout ());
        jf.add (ip, BorderLayout.CENTER);
        jf.setSize (400, 400); 
        jf.setLocation (150, 150);
        jf.setVisible (true);
        jf.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
    }
}

Scaling doesn't work yet, but here you have something to start. (Note that I renamed the image).

Upvotes: 1

Goblin Alchemist
Goblin Alchemist

Reputation: 827

Consider using JLabel for displaying images.

JLabel myLabel=new JLabel();
myLabel.setIcon(new ImageIcon("C:\\tmp\\axiuser\\Pictures\\CLA0014.png"));

Upvotes: 0

user268396
user268396

Reputation: 11986

Without knowing when your program will actually invoke paintComponent() it's impossible to tell. But if you call your loadImage method after you have already shown the GUI (setVisible) you would need to invoke repaint() or invalidate() on the panel in order to trigger a repaint of the component (and update the GUI that way).

Upvotes: 0

Sorin
Sorin

Reputation: 1985

I think you should set the panel as not opaque:

setOpaque(false)

Upvotes: 0

nIcE cOw
nIcE cOw

Reputation: 24626

Just override getPreferredSize() of your JPanel, as you are doing with paintComponent(...) method. Let it return some Dimension object, something like : 

public Dimension getPreferredSize()
{
    return (new Dimension(300, 300));
}

That will allow you to see your images.

Upvotes: 1

Wojciech Owczarczyk
Wojciech Owczarczyk

Reputation: 5735

Maybe there is no Reader defined for *.png.You can check the list of available image readers using ImageIO.getReaderFormatNames()

Upvotes: 0

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