Werner Randelshofer's Blog

As mentioned in an earlier article, I have written a reader for JPEG images with CMYK color data in Java.

This reader can be used with Java ImageIO. I have made a demo including source code: CMYKDemo.jar. You can download this file and then double click it to run the demo. The demo is a window onto which you can drop a CMYK image. You can unzip the file to get the source code.

Here is how to use the CMYKJPEGImageReader with ImageIO:

1. Register the reader with ImageIO.This can be done by putting the file CMYKDemo.jar into the class path.Alternatively – if you want to build the reader from source and integrate it into your own .jar file – you can create a file named META-INF/services/javax.imageio.spi.ImageReaderSpi and put it in the class path.

   The file should contain the following line:

   ch.randelshofer.media.jpeg.CMYKJPEGImageReaderSpi

2. Read an image with ImageIO.Unfortunately, the ImageIO.read method is not a reliable way for reading a JPEG CMYK image.

   ImageIO.read(file);

   This does not work, because ImageIO already provides a JPEG image reader. There is no way to specify in which order the readers shall be used. So, sometimes, ImageIO will use our CMYKJPEGImageReader and succeed, and sometimes it will try to use its own reader, and fail.

   Therefore, we need to use the following code snippet, which tries out all JPEG readers until it succeeds.

   Image img = null;
   ImageInputStream iis = new FileImageInputStream(file);
   try {
       for (Iterator<ImageReader> i = ImageIO.getImageReaders(iis); 
            img == null && i.hasNext(); ) {
           ImageReader r = i.next();
           try {
               r.setInput(iis);
               img = r.read(0);
           } catch (IOException e) {}
       }
   } finally {
       iis.close();
   }
   return img;

As always, my code examples are available for free under the Creative Commons Attribution license. Enjoy.

Update 2014-01-22:
I have closed the comment section for this article, because the CMYKJPEGImageReader class is obsolete. Take a look at the Monte Media Library for newer versions of this class.

I am working on a new AVIWriter class, which provides a higher level API than the  AVIOutputStream class.

There is still a long way to go, so I decided to write a screen recorder as a demo for the upcoming class.

Screen Recorder

This recorder uses java.awt.Robot to capture the screen, and java.awt.MouseInfo for capturing the mouse cursor.

Screen changes are captured with a frame rate of up to 15 fps. Mouse cursor movements with up to 30 fps.

For encoding the videos with AVI, I have implemented the Techsmith Screen Capture Codec in pure Java. This codec is essentially the Microsoft RLE encoder with ZIP compression applied to each video frame.
To play back a recorded video, you may have to install the free codec from www.techsmith.com.

For QuickTime, the videos are encoded with the Apple Animation codec, which I already had implemented some time ago.

You can download the file ScreenRecorder.jar. Double click the file to start the screen recorder. The .jar file also includes the source code of the recorder. The code is preliminary, and may substantially change in future releases.

Update 2012-02-04:

A newer version of the screen recorder is available at http://www.randelshofer.ch/monte

Update 2012-01-13:

The code described in this article is obsolete. Stay tuned for a new recorder which also supports audio capture in AVI files.

Update 2011-07-05:

The rate of screen and mouse captures can now be adjusted individually.

Update 2011-05-13:

I have added support for audio capture. This feature is currently only available with QuickTime videos, since AVIWriter is not finished yet. Audio is recorded from line-in. Line-in is usually the microphone of the computer.

Update 2011-05-09:

I have changed the code so that it will record into the home folder “Videos” on Windows, and into  “Movies” on Mac OS X and everywhere else. In the prior version, recording silently failed if this folder did not exist. Now, an error message is displayed.

Update 2014-01-22:
I have closed the comment section for this article, because the screen recorder class is obsolete. Take a look at the Monte Media Library for newer versions.

In my article ‘Writing QuickTime videos in pure Java’, I said I would integrate audio support if I would get the right incentives (wine or books). This has happened, and so I have implemented an all new class named QuickTimeWriter, which supports writing of audio and video data into a QuickTime Movie file in pure java.

The JavaDoc of the QuickTimeWriter class is available here.

The class is still in a very early stage. Right now, it can be used for combining a single audio track with a single video track.

Audio has to be encoded before it can be written. I tried to make this as simple as possible by supporting javax.sound.sampled.AudioFormat in one of the addAudioTrack() methods.

As with my previous implementation, QuickTimeWriter provides a minimal set of encoders for video data. It includes encoders for the following compression formats: PNG, Photo-JPEG, Apple Animation (RLE) and None (Raw). Other encodings are possible, but you have to encode the frames by yourself.

QuickTimeWriter stores samples in the same sequence in the movie file as they are written. If a movie is created for further processing, the samples can be written in any order. If the movie shall be playable, samples of multiple tracks should be interleaved about twice per second. I have described this in more detail in the class comments.

I have also created a small demo program which shows how to put it all together:

Screenshot of the QuickTimeWriter demo application.

The demo along with all the source files can be downloaded here: QuickTimeDemo2.jar.

The code can be licensed under Creative Commons Attribution 3.0.

Update 2012-02-04: The demo code described in this article is obsolete. The latest version of the code is available on the following page: http://www.randelshofer.ch/monte

Update 2011-01-07: Supports now web-optimized movies with compressed header at the start of the file.

Update 2011-01-06: Supports now Apple Animation (RLE) compression.

Update 2011-01-04: Supports now MP3 sound files.