上载JSP后缩放图像

Question

I need to know how i can scale the uploaded images and save it on the server in the Upload folder.

I have this to process the the form where people can upload there files.

public void init() {
    fileSavePath = getServletContext().getRealPath("/") + File.separator + UPLOAD_DIRECTORY;/*save uploaded files to a 'Upload' directory in the web app*/
    if (!(new File(fileSavePath)).exists()) {
        (new File(fileSavePath)).mkdir();    // creates the directory if it does not exist        
    }
}


public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, java.io.IOException {


        String resp = "";
        int i = 1;
        resp += "<br>Here is information about uploaded files.<br>";
        try {
            MultipartParser parser = new MultipartParser(request, 1024 * 1024 * 1024);  /* file limit size of 1GB*/
            Part _part;
            while ((_part = parser.readNextPart()) != null) {
                if (_part.isFile()) {
                    FilePart fPart = (FilePart) _part;  // get some info about the file
                    String name = fPart.getFileName();
                    if (name != null) {
                        long fileSize = fPart.writeTo(new File(fileSavePath));
                        resp += i++ + ". " + fPart.getFilePath() + "[" + fileSize / 1024 + " KB]<br>";
                    } else {
                        resp = "<br>The user did not upload a file for this part.";
                    }
                }
            }// end while 
        } catch (java.io.IOException ioe) {
            resp = ioe.getMessage();
        }
        request.setAttribute("message", resp);
        getServletContext().getRequestDispatcher("/index.jsp").forward(request, response);
    }

For example i need to rezise all the image to 100x100

Answer 1

First save it, then load it, then scale, then resave it.

try 
{
    BufferedImage img = ImageIO.read(new File(in_path));
    Image scaled = img.getScaledInstance(100, 100, Image.SCALE_FAST);
    ImageIO.write(scaled, "png", out_path);
}
catch (Exception ex)
{
    System.out.println(ex.getMessage();
}

See http://docs.oracle.com/javase/7/docs/api/java/awt/Image.html for list of scaling methods that can be used in the third parameter of getScaledInstance