How to save a image file in java?

Question

I'm developing a QR generator app in java.This is the generating code,

try {

            ByteArrayOutputStream out = QRCode.from(txt_input.getText()).to(ImageType.PNG).stream();
            ByteArrayInputStream in = new ByteArrayInputStream(out.toByteArray());

            BufferedImage image = ImageIO.read(in);

            lbl_output.setIcon(null);
            lbl_output.setIcon(new ImageIcon(image));

            String pic = "image";

        } catch (Exception e) {
            JOptionPane.showMessageDialog(null, " Please enter valid text !");
        }

After generate the QR image I need to save it.So I used this code,

JFileChooser save = new JFileChooser();
int response = save.showSaveDialog(null);

            if (response == JFileChooser.APPROVE_OPTION) {
               try {
                    File fileToSave = new File(pic + ".png");
                    ImageIO.write(image, "PNG", fileToSave);

                } catch (Exception e) {

                }
             }

But there is an exception like,

java.lang.IllegalArgumentException: image == null!
    at javax.imageio.ImageTypeSpecifier.createFromRenderedImage(ImageTypeSpecifier.java:925)
    at javax.imageio.ImageIO.getWriter(ImageIO.java:1591)
    at javax.imageio.ImageIO.write(ImageIO.java:1520)

don't leave catch block empty.use `printStackTrace();` to see if a error is occurred. — Madhawa Priyashantha, Apr 12 '15 at 10:35
@OptimasePrime `BufferedImage image = ImageIO.read(in);` - you know this declares a new variable called "image", which is different from any other variables that happen to be called "image", right? — user253751, Apr 12 '15 at 10:57
`String pic = "image";` <- also, what is this supposed to do? — user253751, Apr 12 '15 at 11:12
You claim to get stack trace of error, but your code doesn't contain any elements which could print it which can be little confusing. To get better answers and sooner post [short but complete code which will let us reproduce your problem](http://sscce.org/). — Pshemo, Apr 12 '15 at 12:31

score 1 · Answer 1 · answered Apr 12 '15 at 15:21

There's no reason to use ImageIO here, because your QRCode class already writes the image in PNG format to an array of bytes.

Instead, just copy the bytes to the file you want.

I.e.:

ByteArrayOutputStream out = QRCode.from(txt_input.getText()).to(ImageType.PNG).stream();
byte[] bytes = out.toByteArray();

...

FileChooser save = new JFileChooser();
int response = save.showSaveDialog(null);

if (response == JFileChooser.APPROVE_OPTION) {
    File fileToSave = new File(pic + ".png");

    // Try-with-resource
    try (OutputStream out = new FileOutputStream(fileToSave)) {
        out.write(bytes);
        out.flush();
    }
}

How to save a image file in java?

1 Answers1