javacv心得，每隔n幀抓一張圖
javacv新手，從網上找的大神寫好的程式碼，但是沒有自己想要的效果，對程式碼進行小修改之後實現了想要的功能。

package com.soft;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import org.bytedeco.javacpp.opencv_core;
import org.bytedeco.javacpp.opencv_core.IplImage;
 

import org.bytedeco.javacpp.presets.opencv_highgui;
import org.bytedeco.javacv.FFmpegFrameGrabber;
import org.bytedeco.javacv.Frame;
import org.bytedeco.javacv.FrameGrabber.Exception;
import org.bytedeco.javacv.Java2DFrameConverter;
import org.bytedeco.javacv.OpenCVFrameConverter;

/**
 * javacv
 * 
 * @author 春曉
 *
 */
 

// D:\javatest\testvideo D:\javatest\c
public class FrameGrabberKit {
	/*
	 * static int num=0; static String name="test"+num;
	 */
	public static void main(String[] args) throws Exception {
		System.out.println(System.getProperty("java.library.path"));
		try {
			fetchFrame("D:/javatest/testvideo/test01.mp4"
 
);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	/**
	 * 獲取指定視訊的幀並儲存為圖片至指定目錄
	 * 
	 * @param videofile
	 *            源視訊檔案路徑
	 * @param framefile
	 *            擷取幀的圖片存放路徑
	 * @throws Exception
	 * @throws IOException
	 */
	public static void fetchFrame(String videofile) throws Exception, IOException {
		FFmpegFrameGrabber ff = new FFmpegFrameGrabber(videofile);
		ff.start();
		ff.getAudioChannels();
		String rotate = ff.getVideoMetadata("rotate");// 視訊的旋轉角度
		int lenght = ff.getLengthInFrames();
		System.out.println("lenght:" + lenght);
		int i = 0;
		int j = 1;
		Frame f = null;
		while (i < lenght) {
			// 過濾前5幀，避免出現全黑的圖片，依自己情況而定
			//每一千幀生成一張圖片保留，若顯示幀不為關鍵幀，則尋找相鄰的下一幀，
			//因為是空迴圈，所以把總長度lenght減一
			f = ff.grabFrame();
			if ((i % 1000) == 0 && i > 5) {
				while (f.image == null) {
					f = ff.grabFrame();
					lenght = lenght - 1;
				}
				if (f.image != null) {
					IplImage src = null;
					if (null != rotate && rotate.length() > 1) {
						OpenCVFrameConverter.ToIplImage converter = new OpenCVFrameConverter.ToIplImage();
						src = converter.convert(f);
						f = converter.convert(rotate(src, Integer.valueOf(rotate)));
					}
					doExecuteFrame(f, "D:/javatest/testpic/test" + j + ".jpg");
					j++;
				}
			}
			i++;
		}
	}

	public static IplImage rotate(IplImage src, int angle) {
		IplImage img = IplImage.create(src.height(), src.width(), src.depth(), src.nChannels());
		opencv_core.cvTranspose(src, img);
		opencv_core.cvFlip(img, img, angle);
		return img;
	}

	public static void doExecuteFrame(Frame f, String targetFileName) {
		if (null == f || null == f.image) {
			return;
		}
		Java2DFrameConverter converter = new Java2DFrameConverter();
		BufferedImage bi = converter.getBufferedImage(f);
		File output = new File(targetFileName);
		try {
			ImageIO.write(bi, "jpg", output);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

}