Fast, temporary data storage

Question

I'm trying to create a screen capture program that'll take screenshots and save them (in some form or another) and then convert them to a movie once recording is completed (similar to java's example Jpeg to Mov program), and I've come to a performance hit (which I think may end up requiring native calls).
I can capture the screen relatively quickly (15-20 fps; no saving of images), so I've determined my issue is temporarily storing them for later use.
At first, I just tried using ImageIO.write (using various different formats), but that cut my fps in half.
Then I tried temporarily storing the BufferedImages in an array to write later. This worked...for about 10 seconds until the computer I was using ran out of memory.
Then I tried separating the work into 2 threads, one for "reading" (screen capture), one for writing, using a LinkedList that's shared between the two threads (reading places image at the end, writing removes the current head). This worked a little bit longer (lasted 30-45 seconds) with a small fps loss (tolerable), but I again got the out of memory error.
So now I'm starting to try and think outside the box.
I read elsewhere on the web that certain methods to get pixel information weren't performance-friendly, and I ended up using
BufferedImage bi = robot.createScreenCapture(screen);
Raster ras = bi.getData()
int[] rgb = (int[]) ras.getDataElements(0,0,screen.width,screen.height,null);Data from my machine at work:
Screen capture: 0.48 sec (consistently)
ImageIO.write: 1.00 - 1.9 sec (depending on format, jpg being the fastest, but at a quality loss, PNG being slowest, but maintaining quality)
rgb array: 0.11 sec (consistently)
So I tried various methods of writing the rgb array to a file:
FileWriter: 1.3 - 1.7 sec (see below)
PrintWriter 1.2 sec (consistently)
BufferedWriter out = new BufferedWriter(new FileWriter("test-image.txt"));
out.write(""+rgb[i]+"\n");  //1.3 sec consistently
out.write(""+rgb); //1.7 sec consistently
out.newLine();
PrintWriter o = new PrinterWriter("test-image2.txt");
for(int k:rgb) {
o.println(rgb[k]);
//1.2 sec consistentlyFor now, it looks like the PrintWriter might be the best trade-off between speed and quality (since it's writing the original color values for each pixel, no quality loss).
Just thought I'd see if anyone else knew of any faster/more efficient methods of temporarily storing the data from a screen shot (BufferedImage).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

Answer 1

amp88 wrote:
How does this run?Forget that. Try this. When you run "Screenie Generator" it will create Screenie files which contain the lossless pixel information from your display. It will continue to do this until you forcibly stop it (Ctrl+C or stop it with your IDE). The files it creates are found in a folder called "Screenies" in the directory you run the code from. To convert those files into PNGs run the ScreenieViewer class. Due to the way the generator is operating at the moment (the fact you have to forcibly stop it executing) when you try to convert the files an exception will always be thrown from the Viewer class when it encounters the partial file. Don't worry about this though, it won't stop the Viewer app from exiting cleanly. There are a couple of parameters you can fiddle with in the code. Modifying DELAY_BETWEEN_SCREENSHOTS_MS will change the target time between generating screenshots. 50 ms gives you 20 fps target output. You can have a play about with that and check out your system usage. If you try too low a value you will run into out of memory problems. Modifying WAITING_SCREENIES_THRESHOLD will change how often the program outputs the screenies it has generated. Please give this a go and let me know how you get on. Also, could you provide details of your system (e.g. the resolution you're attempting to capture at, your CPU, hard disk setup, graphics card etc).
Generate output files:
package tester;
import java.awt.AWTException;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class ScreenieGenerator {
     private final int DELAY_BETWEEN_SCREENSHOTS_MS = 50;
     private final int WAITING_SCREENIES_THRESHOLD = 5;
     private Robot robot;
     private Dimension screenDimension;
     private Rectangle screen;
     private File screenshotsDir = new File("Screenies"+File.separatorChar);
     private ExecutorService cachedThreadPool;
     private ConcurrentLinkedQueue<Screenie> screeniesToBeWrittenToDisk = new ConcurrentLinkedQueue<Screenie>();
     public static void main(String[] args) {
          new ScreenieGenerator();
     private ScreenieGenerator() {
          cachedThreadPool = Executors.newCachedThreadPool();
          screenDimension = Toolkit.getDefaultToolkit().getScreenSize();
          try {
               robot = new Robot();
          } catch(AWTException awte) {
               awte.printStackTrace();
               System.exit(1);
          screenshotsDir.mkdirs();
          screen = new Rectangle(screenDimension);
          Timer outputGeneratorTimer = new Timer();
          outputGeneratorTimer.scheduleAtFixedRate(new TimerTask() {
               public void run() {
                    cachedThreadPool.execute(new CaptureScreenshot());
                    int waitingScreenies = screeniesToBeWrittenToDisk.size();
                    if(waitingScreenies > WAITING_SCREENIES_THRESHOLD) {
                         cachedThreadPool.execute(new OutputScreenshot());
          }, 0, DELAY_BETWEEN_SCREENSHOTS_MS);
     private class CaptureScreenshot implements Runnable {
          public void run() {
               BufferedImage bi = robot.createScreenCapture(screen);
               Screenie thisScreenie = new Screenie(bi.getWidth(), bi.getHeight(),
                         bi.getRGB(0, 0, bi.getWidth(), bi.getHeight(), null, 0, bi.getWidth()));
               screeniesToBeWrittenToDisk.add(thisScreenie);
     private class OutputScreenshot implements Runnable {
          public void run() {
               if(screeniesToBeWrittenToDisk.size() > 0) {
                    try {
                         Screenie screenie = screeniesToBeWrittenToDisk.remove();
                         ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(
                                   screenshotsDir.getAbsolutePath()+
                                   File.separatorChar+System.nanoTime()+".screenie"));
                         oos.writeObject(screenie);
                         oos.close();
                    } catch(IOException ioe) {
                         ioe.printStackTrace();
}Convert outputted files from program above to PNG files:
package tester;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import javax.imageio.ImageIO;
public class ScreenieViewer {
     File screeniesDirectory = new File("Screenies/");
     public static void main(String[] args) {
          new ScreenieViewer();
     private ScreenieViewer() {
          if(!screeniesDirectory.exists()) {
               print("Screenies directory doesn't exist: "+screeniesDirectory.getAbsolutePath());
               System.exit(1);
          int filesConverted = 0;
          File[] allScreeniesFiles = screeniesDirectory.listFiles();
          if(allScreeniesFiles == null || allScreeniesFiles.length == 0) {
               print("no screenie files to convert!");
               System.exit(0);
          for(File oneScreenie : allScreeniesFiles) {
               if(oneScreenie.getAbsolutePath().endsWith(".screenie")) {
                    print("found a screenie file to convert: "+oneScreenie.getAbsolutePath());
                    try {
                         outputOneFileAsPNG(oneScreenie.getAbsolutePath());
                         filesConverted++;
                    } catch(IOException ioe) {
                         print("IOException attempting to output file: "+oneScreenie.getAbsolutePath());
                         ioe.printStackTrace();
                    } catch(ClassNotFoundException cnfe) {
                         cnfe.printStackTrace();
                         System.exit(1);
          print(filesConverted+" screenie files converted");
          print(this.getClass().getSimpleName()+" exiting");
     private void outputOneFileAsPNG(String inputFilename) throws ClassNotFoundException, IOException {
          BufferedImage screenieImage = getBufferedImageForInputScreenie(inputFilename);
          String outputFilename = inputFilename;
          outputFilename = outputFilename.substring(0, outputFilename.lastIndexOf("."))+".png";
        ImageIO.write(screenieImage, "png", new File(outputFilename));
        print("successfully outputted screenie file: "+outputFilename);
     private BufferedImage getBufferedImageForInputScreenie(String inputFilename) throws IOException, ClassNotFoundException {
          ObjectInputStream ois = new ObjectInputStream(new FileInputStream(inputFilename));
          Screenie screenie = (Screenie) ois.readObject();
          BufferedImage screenieImage = new BufferedImage(screenie.getWidth(), screenie.getHeight(), BufferedImage.TYPE_INT_ARGB);
          screenieImage.setRGB(0, 0, screenie.getWidth(), screenie.getHeight(), screenie.getData(), 0, screenie.getWidth());
          return screenieImage;
     private void print(String msg) {
          System.out.println(msg);
}The output file object:
package tester;
import java.io.Serializable;
public class Screenie implements Serializable {
     private static final long serialVersionUID = 1289508155211323563L;
     private int width, height;
     private int[] data;
     public Screenie(int width, int height, int[] data) {
          this.width = width;
          this.height = height;
          this.data = data;
     public int getWidth() {
          return width;
     public int getHeight() {
          return height;
     public int[] getData() {
          return data;
}