Zoom in and out of images in Java

Question

I think the question is quite self-explanatory. I want to implement a simple zoom function using a JSlider like in Windows Live Photo Gallery for instance.

I've had a quick look online but all the code I've tried to use appears to have errors when I copy it into Eclipse. I don't really want to use a third-party library either as the application may be sold under a company name. Plus, I'm beginning to realise that there may be some safety precautions required in order to prevent errors, but I do not know what these will be.

So, if anybody can provide me with some Java code to zoom in and out of images it would be greatly appreciated.

PS I plan to use the Image as an ImageIcon inside of a JLabel which will be added to a JScrollPane .

Answer 1

You can easily achieve this by using scale transforms on the original image. Assuming your the current image width newImageWidth , and the current image height newImageHeight , and the current zoom level zoomLevel , you can do the following:

int newImageWidth = imageWidth * zoomLevel;
int newImageHeight = imageHeight * zoomLevel;
BufferedImage resizedImage = new BufferedImage(newImageWidth , newImageHeight, imageType);
Graphics2D g = resizedImage.createGraphics();
g.drawImage(originalImage, 0, 0, newImageWidth , newImageHeight , null);
g.dispose();

Now, replace the original image, originalImage , in your display area by resizedImage .

Answer 2

You can also use it as follows :

public class ImageLabel extends JLabel{
    Image image;
    int width, height;

    public void paint(Graphics g) {
        int x, y;
        //this is to center the image
        x = (this.getWidth() - width) < 0 ? 0 : (this.getWidth() - width);
        y = (this.getHeight() - width) < 0 ? 0 : (this.getHeight() - width);

        g.drawImage(image, x, y, width, height, null);
    }

    public void setDimensions(int width, int height) {
        this.height = height;
        this.width = width;

        image = image.getScaledInstance(width, height, Image.SCALE_FAST);
        Container parent = this.getParent();
        if (parent != null) {
            parent.repaint();
        }
        this.repaint();
    }
}

Then you can put it to your frame and with the method that zooms with a zooming factor, for which I used percent values.

public void zoomImage(int zoomLevel ){
    int newWidth, newHeight, oldWidth, oldHeight;
    ImagePreview ip = (ImagePreview) jLabel1;
    oldWidth = ip.getImage().getWidth(null);
    oldHeight = ip.getImage().getHeight(null);

    newWidth = oldWidth * zoomLevel/100;
    newHeight = oldHeight * zoomLevel/100;

    ip.setDimensions(newHeight, newWidth);
}