Question

I am attempting to read in a stream and save the read images to a zip file as this is going to be running over multiple days and would generate far too many individual files.

I now have an issue where I seem to be unable to save images into a zip file. The worker thread I have built for it is below. I am sure that the image is making it to the ImageIO.write. The result at the end however is a zip file of empty jpgs. I am wondering if perhaps ImageIO is not writing property to the ZipOutputStream.

Thanks for your help.

public class ZipSaveWorker implements Runnable{

    public static ZipOutputStream out=null;
    BufferedImage myImage;
    private static int counter=0;



    public void run() {
        ZipEntry entry=new ZipEntry("video"+counter+".jpg");
        counter++;
        try {
            out.putNextEntry(entry);
            ImageIO.write(myImage, ".jpg", out);

        } catch (IOException ex) {
            Logger.getLogger(ZipSaveWorker.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    public ZipSaveWorker(BufferedImage image)
    {
        if (out==null)
        {
            try {
                out = new ZipOutputStream(new BufferedOutputStream(new FileOutputStream(new File("images" + File.separator + "video.zip"))));
            } catch (FileNotFoundException ex) {
                Logger.getLogger(ZipSaveWorker.class.getName()).log(Level.SEVERE, null, ex);
            }
            counter=0;
        }

        myImage=image;

    }

    public static void closeStream()
    {
        try {
            out.flush();
            out.close();
        } catch (IOException ex) {
            Logger.getLogger(ZipSaveWorker.class.getName()).log(Level.SEVERE, null, ex);
        }
    }


}

Answer 1

The error in your code is in the line:

ImageIO.write(myImage, ".jpg", out);

It should be:

ImageIO.write(myImage, "jpg", out);

I am also not sure if you should call closeEntry() after every image has been written.

Consider what Stephen C writes, this code could result in corrupt zip files if the power was cut or the VM died. Consider making backups of the zip files a few times a week, maybe even a few times a day, to ensure your multiple day runs aren’t completely ruined (I assume a run can be resumed).