Multimedia
(Submitted by Nelson Yu)
There are two main ways to play an .au file in an applet(in a stand-alone
application you will need to use the undocumentated sun.* classes or write
your own audio handler).
1) Play the audio directly
play(URL)
play(URL, string)
// say audio file is located at http://java.sun.com/
// which is the documentation base
play(getDocumentBase(), "myLittleAudio.au");
otherwise if its located in a 'audio' directory you will need create a new
url i.e
URL u = new URL(getDocumentBase().toString() + "/audio");
2) Get the audio clip then play it later(or have it loop)
getAudioClip(URL)
getAudioClip(URL, string)
used in the same manner as above, but instead it will return an AudioClip(which
is an interface) in much the same way as getAppletContext() returns
an AppletContext even though AppletContext is an interface.
getAudioClip(getDocumentBase(), "myLittleAudio.au").loop();
(Submitted by William S. Clark)
This will play an .au file:
import java.io.InputStream;
import java.net.*;
import java.applet.*;
import java.awt.Graphics;
import java.awt.Color;
public class Message extends java.applet.Applet {
private String file;
private AudioClip source;
public void init() {
setBackground(new Color(0));
file=getParameter("FILE");
source=getAudioClip(getDocumentBase(),file);
}
public void start() {
if(source!=null) source.play();
}
public void stop() {
if(source!=null) source.stop();
}
}
(Submitted by Steve Alexander)
Using the AudioClip class and several Applet-specific methods,
it is quite easy to retrieve and play an ".au" audio file.
The code sample below is not robust (exception handling and
null-checking are not present) but it is a simple example of
the basic process involved in getting an audio object, and
playing that file.
The key objects and methods used are AudioClip, loop() and stop().
Another method not used here but perhaps of some value is the
play() method which plays an audio clip one time.
import java.applet.Applet;
import java.applet.AudioClip;
import java.awt.*;
public class PlayAudio extends Applet
{
AudioClip myAudio;
Button b_play;
Button b_stop;
String textString;
public void init()
{
resize(300, 100);
b_play = new Button("Play audio");
b_stop = new Button("Stop audio");
myAudio = getAudioClip(getDocumentBase(), "computer.au");
add(b_play);
add(b_stop);
}
public void start()
{
}
public void paint(Graphics g)
{
g.setColor(Color.blue);
g.drawString(textString, 100,75);
}
public boolean action(Event e, Object arg)
{
if(e.target instanceof Button)
{
if("Play audio" == arg)
{
myAudio.loop();
textString = "Playing audio...";
}
if("Stop audio" == arg)
{
myAudio.stop();
textString = "Not playing audio...";
}
}
repaint();
return true;
}
}
(Submitted by Hui Zhao Wang, and others)
To convert .wav to .au files, check out
GoldWave 2.14 (not the latest version which writes invalid .au files).
It's available from :
http://www.cs.mun.ca/~chris3/goldwave/
(Submitted by Mike Hippolyte)
The Java MIDI software is at
http://www.interport.net/~mash/javamidi.html
and a keyboard applet that uses Java MIDI is at
http://www.interport.net/~mash/midikeyboard.html.
(Submitted by Jeff Harrington)
You can use Csound, a digital audio compiler, to convert MIDI
files to .wav files. From .wav files you can use Sox
or another converter program. Csound is available
here. I've got
a demo of Csound audio and a Java applet at
my site.
How many sound channels do I have in Java?
How does one (use Toolkit.sync() to?) flush the buffer of things to be drawn and hence
bring the display up to date?
(Submitted by Adam Moss)
getToolkit().sync().
However, in a tight loop there seems to be a high performance hit
on Windows95, particularly in terms of event-passing.
How do I play a .avi file?
How do I get an applet to sleep until an image has loaded?
(Submitted by John Zukowski)
MediaTracker tracker;
image = getImage (getDocumentBase(), "image.jpg");
tracker = new MediaTracker (this);
tracker.addImage (image, 0);
// waitForAll will block the ENTIRE applet
try { tracker.waitForAll();} catch (Exception e) {}
(Submitted by Bryan Smith)
The java.awt.MediaTracker class can be used to suspend applet execution
until an image or series of images has been loaded, as in the following
code segment:
public class ImageLoadingApplet extends Applet
{
Image img;
MediaTracker img_tracker;
...
public void init()
{
img_tracker = new MediaTracker(this);
// Start loading image and register it
// with the MediaTracker object.
img = getImage(getCodeBase, "images/img.gif");
img_tracker.add(img,0);
// Wait until image loaded before proceeding.
try
{
img_tracker.waitForID(0);
}
catch (InterruptedException e)
{
// exception handling
}
...
}
...
}
A more in-depth example of the use of MediaTracker is in Sun's API
documentation at:
http://java.sun.com/JDK-1.0/api/java.awt.MediaTracker.html.
(Submitted by Guohua Li)
Check out my homepage. I have source code there:
http://enuxsa.eas.asu.edu/~guohua.
(Submitted by Jeff Marin)
MemoryImageSource has six constructors, all of which take either
an array of int of BYTE. Just remember, after you create an instance
of MemoryImageSource, to actually create an image you must do the
following:
Image m_RotImage = createImage(
new MemoryImageSource(m_width, m_height, pix_dest, 0, m_width));
(Submitted by Anujit Sarkar)
import java.awt.*;
import java.awt.image.*;
public class ImageWindow extends Frame
{
Image im=null;
public ImageWindow()
{
}
public void createImage()
{
im = getToolkit().getImage("b01.gif");
}
public void paint(Graphics g)
{
update(g);
}
public void update(Graphics g)
{
g.drawImage(im, 0, 0, this);
}
public boolean handleEvent(Event evt)
{
if (evt.id == Event.WINDOW_DESTROY)
{
System.exit(0);
}
return super.handleEvent(evt);
}
public static void main(String args[])
{
ImageWindow window = new ImageWindow();
window.createImage();
window.setTitle("Java StandAlone Application");
window.pack();
window.resize(500,300);
window.show();
}
}
(Submitted by Kelvin Ho)
The following is a sample program which can load an image into an application.
import java.awt.*;
public class Holder extends Frame
{
Holder ()
{
MyPicture pic = new MyPicture ();
add (pic);
resize (500,500);
}
public boolean handleEvent(Event evt)
{
if (evt.id == Event.WINDOW_ICONIFY) {//DOESN'T seem to be necessary
hide();
return true;
}
if (evt.id == Event.WINDOW_DESTROY) {
System.exit(0);
}
return super.handleEvent(evt);
}
public static void main (String args[])
{
Holder window = new Holder ();
window.setTitle("Java's Duke");
window.pack();
window.show();
}
}
class MyPicture extends Panel
{
Image img;
MyPicture ()
{
super ();
resize (100, 100);
img = Toolkit.getDefaultToolkit().getImage("T1.gif");
repaint ();
}
public void paint (Graphics g)
{
g.drawImage(img, 10, 10, this);
}
}
(Submitted by David Gibbons)
This is a "hack" to get around a bug in 1.0beta2 Java that will not allow
image loading from a java application with the getImage method.
add:
import sun.awt.image.FileImageSource // the sun classes are included
// in the current sdk
create a SecurityManager class with the following methods:
class SecMan extends SecurityManager{
public checkRead(String s){return;}
public checkPropertyAcess(String s){return;}
public checkLink(String s){return;}
public checkAccess(Thread t){return;}
public checkAccess(ThreadGroup tg){return;}
public checkExit(int i){return;}
}
make this visible to the entire class:
Image im;
somewhere like main or init insert this:
...
SecMan secMan = new SecMan();
System.setSecurityManager(secMan);
Canvas cs = new Canvas();
im = cs.createImage(new FileImageSource("your.gif"));
...
put this call in your paint:
public void paint(Graphics p){
...
g.drawImage(im, 0, 0, this);
...
This should do it until the problem is fixed.
(Submitted by Beat Liechti)
Here's at least how to write a GIF from an Image:
http://www.cs.brown.edu/people/amd/java/GIFEncoder/
(Submitted by Andrew Wilkinson)
One simple way is to pass the bacground color of the HTML page as a parameter into
the applet.
In the HTML:
<html>
<body bgcolor="#3399CC">
<applet code=TrnsBgrnd height=200 width=250>
<param name=bgcolor value="3399CC">
</applet>
</body>
</html>
In the Java Code:
import java.applet.Applet;
import java.awt.*;
public class TrnsBgrnd extends Applet {
Color bgcolor=null;
public void init() {
// Read the value of the parameter bgcolor and set the applet
// background to this value.
String attr = getParameter("bgcolor");
bgcolor = (attr != null) ? convertColor(attr) : Color.white;
setBackground(bgcolor);
}
public Color convertColor(String colStr) {
int rd = (Integer.valueOf(colStr, 16).intValue() & 0xFF0000) >> 16 ;
int gn = (Integer.valueOf(colStr, 16).intValue() & 0xFF00) >> 8;
int bl = Integer.valueOf(colStr, 16).intValue() & 0xFF ;
return (new Color(rd, gn, bl));
}
public void paint(Graphics g) {
// Do what every graphics processing is required.
g.drawRect(50, 50, 150, 100);
}
}
(Submitted by Jim Crossley)
/*
* To determine when an image has finished loading, use the prepareImage()
* method of Component (of which Applet is a subclass). This causes
* the "image-getting" thread to call imageUpdate() whenever something
* interesting happens, i.e. the image finishes loading. We override
* imageUpdate() and set a "ready" flag when we have "all of the bits".
*/
import java.applet.*;
import java.awt.*;
public class Testing extends Applet {
Image image;
boolean ready = false;
public void init() {
image = this.getImage(this.getDocumentBase(), "image.gif");
// now tell the "image-getting" thread to call imageUpdate()
this.prepareImage(image,this);
}
public boolean imageUpdate(Image img, int infoflags, int x, int y, int w,
int h) {
if ((infoflags & ALLBITS) != 0) {
ready = true;
repaint();
return false;
}
else
return true;
}
public void paint(Graphics g) {
if (ready)
g.drawImage(image,0,0,this);
}
}
(Submitted by the editor)
As of Netscape 2.01, you must now use:
img = getImage(getDocumentBase(), "image.gif");