我正在努力从视频中生成缩略图。我能够做到，但我只需要一个视频中的缩略图，但我得到的是视频不同时间的不止一个图像。我使用以下代码生成缩略图。请建议我应该在下面的代码中修改什么，以便从视频的中间部分只获得一个缩略图。我使用的代码如下（我使用过 Xuggler ）：
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import com.xuggle.mediatool.IMediaReader;
import com.xuggle.mediatool.MediaListenerAdapter;
import com.xuggle.mediatool.ToolFactory;
import com.xuggle.mediatool.event.IVideoPictureEvent;
import com.xuggle.xuggler.Global;
public class Main {
public static final double SECONDS_BETWEEN_FRAMES = 10;
private static final String inputFilename = "D:\\k\\Knock On Wood Lesson.flv";
private static final String outputFilePrefix = "D:\\pix\\";
// The video stream index, used to ensure we display frames from one and
// only one video stream from the media container.
private static int mVideoStreamIndex = -1;
// Time of last frame write
private static long mLastPtsWrite = Global.NO_PTS;
public static final long MICRO_SECONDS_BETWEEN_FRAMES =
(long) (Global.DEFAULT_PTS_PER_SECOND * SECONDS_BETWEEN_FRAMES);
public static void main(String[] args) {
IMediaReader mediaReader = ToolFactory.makeReader(inputFilename);
// stipulate that we want BufferedImages created in BGR 24bit color space
mediaReader.setBufferedImageTypeToGenerate(BufferedImage.TYPE_3BYTE_BGR);
mediaReader.addListener(new ImageSnapListener());
// read out the contents of the media file and
// dispatch events to the attached listener
while (mediaReader.readPacket() == null);
}
private static class ImageSnapListener extends MediaListenerAdapter {
public void onVideoPicture(IVideoPictureEvent event) {
if (event.getStreamIndex() != mVideoStreamIndex) {
// if the selected video stream id is not yet set, go ahead an
// select this lucky video stream
if (mVideoStreamIndex == -1) {
mVideoStreamIndex = event.getStreamIndex();
} // no need to show frames from this video stream
else {
return;
}
}
// if uninitialized, back date mLastPtsWrite to get the very first frame
if (mLastPtsWrite == Global.NO_PTS) {
mLastPtsWrite = event.getTimeStamp() - MICRO_SECONDS_BETWEEN_FRAMES;
}
// if it's time to write the next frame
if (event.getTimeStamp() - mLastPtsWrite
>= MICRO_SECONDS_BETWEEN_FRAMES) {
String outputFilename = dumpImageToFile(event.getImage());
// indicate file written
double seconds = ((double) event.getTimeStamp())
/ Global.DEFAULT_PTS_PER_SECOND;
System.out.printf("at elapsed time of %6.3f seconds wrote: %s\n",
seconds, outputFilename);
// update last write time
mLastPtsWrite += MICRO_SECONDS_BETWEEN_FRAMES;
}
}
private String dumpImageToFile(BufferedImage image) {
try {
String outputFilename = outputFilePrefix
+ System.currentTimeMillis() + ".png";
ImageIO.write(image, "png", new File(outputFilename));
return outputFilename;
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
}
}