Saving a captured image in Java ME
This code example demonstrates how to take a picture by camera and save it to file.
Article Metadata
Code Example
Source file: Media:SavingCapturedImage.zip
Tested with
Devices(s): Nokia E70, Nokia C3-01, Nokia Asha 306, Nokia E7-00
Compatibility
Platform(s): Series 40, S60, Nokia Belle
Article
Keywords: javax.microedition.media.Manager, javax.microedition.media.Player, javax.microedition.media.control.VideoControl, javax.microedition.media.Manager.createPlayer, javax.microedition.media.Player.getControl, javax.microedition.media.control.VideoControl.getSnapshot
Created: dekudin
(27 Nov 2008)
Last edited: hamishwillee
(05 Oct 2012)
Contents |
Overview
Perform the following steps:
- Check support of video capturing by calling the System.getProperty method with the supports.video.capture parameter.
- Call Manager.createPlayer method to create a camera player.
- Initialize and start player.
- Get VideoControl object from the player and execute the VideoControl.getSnaphot method. This method returns array of bytes which represents captured image in specified format.
- Open file and send array of bytes to it. After this, the file should be closed.
- On exit from application, the camera player will be stopped and closed.
Source file: CaptureAndSaveImage.java
import javax.microedition.midlet.MIDlet;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.Item;
import javax.microedition.lcdui.Alert;
import javax.microedition.media.Manager;
import javax.microedition.media.Player;
import javax.microedition.media.control.VideoControl;
import javax.microedition.media.MediaException;
import javax.microedition.io.Connector;
import javax.microedition.io.file.FileConnection;
import java.io.OutputStream;
import java.io.IOException;
public class CaptureAndSaveImage extends MIDlet implements CommandListener {
private Display display;
// Form where camera viewfinder is placed
private Form cameraForm;
// Command for capturing image by camera and saving it.
// Placed in cameraForm.
private Command cmdCapture;
// Command for exiting from midlet. Placed in cameraForm.
private Command cmdExit;
// Player for camera
private Player player;
// Video control of camera
private VideoControl videoControl;
// Alert to be displayed if error occurs.
private Alert alert;
/**
* Constructor.
*/
public CaptureAndSaveImage() {
InitializeComponents();
}
/**
* Initializes components of midlet.
*/
private void InitializeComponents() {
display = Display.getDisplay(this);
if(checkCameraSupport() == false) {
showAlert("Alert", "Camera is not supported!", null);
return;
}
try {
createCameraForm();
createCamera();
addCameraToForm();
startCamera();
} catch(IOException ioExc) {
showAlert("IO error", ioExc.getMessage(), null);
} catch(MediaException mediaExc) {
showAlert("Media error", mediaExc.getMessage(), null);
}
}
/**
* Creates and returns form where the camera control will be placed.
*/
private void createCameraForm() {
// Create camera form
cameraForm = new Form("Camera");
// Create commands for this form
cmdCapture = new Command("Capture", Command.OK, 0);
cmdExit = new Command("Exit", Command.EXIT, 0);
// Add commands to form
cameraForm.addCommand(cmdCapture);
cameraForm.addCommand(cmdExit);
// Set midlet as command listener for this form
cameraForm.setCommandListener(this);
}
/**
* Check camera support.
* @return true if camera is supported, false otherwise.
*/
private boolean checkCameraSupport() {
String propValue = System.getProperty("supports.video.capture");
return (propValue != null) && propValue.equals("true");
}
/**
* Creates camera control and places it to cameraForm.
*/
private void createCamera() {
try {
player = Manager.createPlayer("capture://image");
}
catch (MediaException e) {
try {
System.out.println("Couldn't set \"capture://video\"");
player = Manager.createPlayer("capture://video");
}
catch (MediaException ex) {
}
catch (IOException ex) {
}
}
catch (IOException e) {
}
try {
player.realize();
player.prefetch();
}
catch (MediaException e) {
}
videoControl = (VideoControl)player.getControl("VideoControl");
}
/**
* Adds created camera as item to cameraForm.
*/
private void addCameraToForm() {
cameraForm.append((Item)videoControl.
initDisplayMode(VideoControl.USE_GUI_PRIMITIVE, null));
}
/**
* Start camera player
* @throws IOException if starting of player is failed.
* @throws MediaException if starting of player is failed.
*/
private void startCamera() throws IOException, MediaException {
if(player.getState() == Player.PREFETCHED) {
player.start();
}
}
/**
* Saves image captured by camera.
*/
private void captureAndSaveImage() {
FileConnection file = null;
OutputStream outStream = null;
try {
if(checkPngEncodingSupport() == false) {
throw new Exception("Png encoding is not supported!");
}
// Capture image
byte[] capturedImageData =
videoControl.getSnapshot("encoding=png");
// Get path to photos folder.
String dirPhotos = System.getProperty("fileconn.dir.photos");
if(dirPhotos == null) {
throw new Exception("Unable get photos folder name");
}
String fileName = dirPhotos + "CapturedImage.png";
// Open file
file = (FileConnection)Connector.open(fileName,
Connector.READ_WRITE);
// If there is no file then create it
if(file.exists() == false) {
file.create();
}
// Write data received from camera while making snapshot to file
outStream = file.openOutputStream();
outStream.write(capturedImageData);
showAlert("Info", "Image is saved in " + fileName, cameraForm);
} catch(IOException ioExc) {
showAlert("IO error", ioExc.getMessage(), cameraForm);
} catch(MediaException mediaExc) {
showAlert("Media error", mediaExc.getMessage(), cameraForm);
} catch(Exception exc) {
showAlert("Error", exc.getMessage(), cameraForm);
} finally {
// Try to close file
try {
if(outStream != null) {
outStream.close();
}
if(file != null) {
file.close();
}
} catch(Exception exc) {
// Do nothing
}
}
}
/**
* Checks png encoding support
* @return true if png encoding is supported false otherwise.
*/
private boolean checkPngEncodingSupport() {
String encodings = System.getProperty("video.snapshot.encodings");
return (encodings != null) && (encodings.indexOf("png") != -1);
}
/**
* From MIDlet.
* Signals the MIDlet that it has entered the Active state.
*/
public void startApp() {
if ( videoControl != null ) {
display.setCurrent(cameraForm);
}
}
/**
* From MIDlet.
* Signals the MIDlet to enter the Paused state.
*/
public void pauseApp() {
// TODO: pause player if it is running.
}
/**
* Performs exit from midlet.
*/
public void exitMIDlet() {
notifyDestroyed();
}
/**
* Shows alert with specified title and text. If next displayable is not
* specified then application will be closed after alert closing.
* @param title - Title of alert.
* @param message - text of alert.
* @param nextDisp - next displayable. Can be null.
*/
private void showAlert(String title, String message, Displayable nextDisp) {
alert = new Alert(title);
alert.setString(message);
alert.setTimeout(Alert.FOREVER);
if(nextDisp != null) {
display.setCurrent(alert, nextDisp);
} else {
display.setCurrent(alert);
alert.setCommandListener(this);
}
}
/**
* From MIDlet.
* Signals the MIDlet to terminate and enter the Destroyed state.
*/
public void destroyApp(boolean unconditional) {
if(player != null) {
player.deallocate();
player.close();
}
}
/**
* From CommandListener.
* Indicates that a command event has occurred on Displayable displayable.
* @param command - a Command object identifying the command.
* @param displayable - the Displayable on which this event has occurred.
*/
public void commandAction(Command command, Displayable displayable) {
// Handles "Capture image" command from cameraForm
if(command == cmdCapture) {
captureAndSaveImage();
}
// Handles "exit" command from forms
if(command == cmdExit) {
exitMIDlet();
}
// Handle "ok" command from alert
if(displayable == alert) {
exitMIDlet();
}
}
}
Postconditions
Camera viewfinder is shown on display.
By choosing "Capture image" menu command, the user can take a snapshot and save it to CapturedImage.png file in photos folder. Image will be saved to file with PNG encoding.
Supplementary material
Executables and source files can be found in Media:SavingCapturedImage.zip.
