一、需求背景

博主的大概需求是，获取第一章第一节的课件（有pdf、各种文档、视频等形式），生成课程的封面图片。

二、引入依赖

        <dependency>
            <groupId>org.bytedeco</groupId>
            <artifactId>javacv</artifactId>
            <version>1.4.1</version>
        </dependency>
        <dependency>
            <groupId>org.bytedeco</groupId>
            <artifactId>javacpp</artifactId>
            <version>1.4.1</version>
        </dependency>
        <dependency>
            <groupId>org.bytedeco.javacpp-presets</groupId>
            <artifactId>ffmpeg-platform</artifactId>
            <version>3.4.2-1.4.1</version>
        </dependency>

三、根据自身的业务编写合适的代码

/**
     * 保存课程信息自动设置课程封面图片
     * @param courseInformation
     * @param coursewareId
     */
    private void setDefaultCourseCoverPhoto(CourseInformation courseInformation, Long coursewareId) {
        String key = "";
        InputStream pdfStream = null;
        PDDocument pdfDocument = null;
        try {
            CoursewareLibrary library = coursewareLibraryMapper.selectById(coursewareId);
            //获取网络流
            String urlByPreviewPdf = documentManagementApiServer.getUrlByPreviewPdf(library.getSourceFileKey());
            pdfStream = ImageUtil.getImageStream(urlByPreviewPdf);
            if (BusinessConstant.COURSEWARE_LIBRARY_VIDEO.equals(library.getCoursewareType()) ||
                    BusinessConstant.COURSEWARE_LIBRARY_AUDIO.equals(library.getCoursewareType())){
                pdfStream = returnBitMap(urlByPreviewPdf);
                //1.生成本地源文件、目的文件
                String source = tempPath + "/source/" + library.getSourceFileKey();
                MultipartFile multipartFile = FileUtil.getMultipartFile(pdfStream, library.getSourceFileKey());
                File file = FileUtil.toFile(multipartFile);
                BufferedImage buffImage = VideoCaptureUtils.generatePhoto(source,file.getPath());
                MultipartFile uploadMultipartFile = fileCase(buffImage);
                key = uploadPhoto(uploadMultipartFile);
                FileUtil.del(file);
                FileUtil.del(source);
            }else if (BusinessConstant.COURSEWARE_LIBRARY_FILE.equals(library.getCoursewareType()) ||
                    BusinessConstant.COURSEWARE_LIBRARY_PDF.equals(library.getCoursewareType())){
                pdfDocument = PDDocument.load(pdfStream);
                //PDFRenderer的类将PDF文档呈现为AWT BufferedImage
                PDFRenderer pdfRenderer = new PDFRenderer(pdfDocument);
                // 提取的页码
                int pageNumber = 0;
                // 以300 dpi 读取存入 BufferedImage 对象
                int dpi = 500;
                //Renderer类的renderImage()方法在特定页面中渲染图像
                BufferedImage buffImage = pdfRenderer.renderImageWithDPI(pageNumber, dpi, ImageType.RGB);
                // 文件类型转换
                MultipartFile multipartFile = fileCase(buffImage);
                key = uploadPhoto(multipartFile);
                // 关闭文档
                pdfDocument.close();
                //删除临时文件
//                        log.info("临时文件的目录："+s);
            }
            courseInformation.setCoverPhotoKey(key);
        }catch (Exception e){
            log.error("{}",e);
            e.printStackTrace();
        }finally {
            IOUtils.closeQuietly(pdfStream);
            IOUtils.closeQuietly(pdfDocument);
        }
    }

    public static MultipartFile getMultipartFile(InputStream inputStream, String fileName) {
        FileItem fileItem = createFileItem(inputStream, fileName);
        return new CommonsMultipartFile(fileItem);
    }


    public static File toFile(MultipartFile multipartFile) {
        String fileName = multipartFile.getOriginalFilename();
        String prefix = "." + getExtensionName(fileName);
        File file = null;

        try {
            file = File.createTempFile(IdUtil.simpleUUID(), prefix);
            multipartFile.transferTo(file);
        } catch (IOException var5) {
            var5.printStackTrace();
        }

        return file;
    }


    /**
     * 将buffImage转换为MultipartFile
     * @param buffImage
     * @return MultipartFile
     */
    private MultipartFile fileCase(BufferedImage buffImage) {
        //得到BufferedImage对象
        // BufferedImage bufferedImage = JoinTwoImage.testEncode(200, 200, url);
        MultipartFile multipartFile= null;
        try {
            //创建一个ByteArrayOutputStream
            ByteArrayOutputStream os = new ByteArrayOutputStream();
            //把BufferedImage写入ByteArrayOutputStream
            ImageIO.write(buffImage, "jpg", os);
            //ByteArrayOutputStream转成InputStream
            InputStream input = new ByteArrayInputStream(os.toByteArray());
            //InputStream转成MultipartFile
            multipartFile =new MockMultipartFile("file", "file.jpg", "text/plain", input);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return multipartFile;
    }

import org.bytedeco.javacv.FFmpegFrameGrabber;
import org.bytedeco.javacv.Frame;
import org.bytedeco.javacv.Java2DFrameConverter;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.util.ArrayList;
import java.util.List;

public class VideoCaptureUtils {

    /**
     *
     * @Title: getTempPath
     * @Description: 生成视频的首帧图片方法
     * @author: Zing
     * @param: @param tempPath 生成首帧图片的文件地址
     * @param: @param filePath 传进来的线上文件
     * @param: @return
     * @param: @throws Exception
     * @return: boolean
     * @throws
     */
    public static BufferedImage generatePhoto(String tempPath, String filePath) throws Exception {
        File targetFile = new File(tempPath);
        if (!targetFile.getParentFile().exists()) {
            targetFile.getParentFile().mkdirs();
        }
        File file2 = new File(filePath);
        BufferedImage bufferedImage = null;
        //判断文件是否为视频
        if(isVideo(filePath)) {
            if (file2.getParentFile().exists()) {
                FFmpegFrameGrabber ff = new FFmpegFrameGrabber(file2);
                ff.start();
                int ftp = ff.getLengthInFrames();
                int flag=0;
                Frame frame = null;
                while (flag <= ftp) {
                    //获取帧
                    frame = ff.grabImage();
                    //过滤前3帧，避免出现全黑图片
                    if ((flag>3)&&(frame != null)) {
                        break;
                    }
                    flag++;
                }
//                if(ImageIO.write(FrameToBufferedImage(frame), "jpg", targetFile)) {
//                    ff.close();
//                    ff.stop();
//                    return true;
//                }else {
//                    ff.close();
//                    ff.stop();
//                    return false;
//                }
                bufferedImage = FrameToBufferedImage(frame);
                ImageIO.write(bufferedImage, "jpg", targetFile);
                ff.close();
                ff.stop();
            }
        }
        return bufferedImage;
    }

    /***
     *
     * @Title: FrameToBufferedImage
     * @Description: 创建格式化BufferedImage对象
     * @author: Zing
     * @param: @param frame
     * @param: @return
     * @return: RenderedImage
     * @throws
     */
    private static BufferedImage FrameToBufferedImage(Frame frame) {
        //创建BufferedImage对象
        Java2DFrameConverter converter = new Java2DFrameConverter();
        BufferedImage bufferedImage = converter.getBufferedImage(frame);
        return bufferedImage;
    }

    /**
     *
     * @Title: isVideo
     * @Description:判断是不是视频
     * @author: Zing
     * @param: @param path 文件路径
     * @param: @return
     * @return: boolean       true是视频 false非视频
     * @throws
     */
    public static boolean isVideo(String path) {
        List<String> typeList = new ArrayList<String>();
        typeList.add("mp4");
        typeList.add("flv");
        typeList.add("avi");
        typeList.add("rmvb");
        typeList.add("rm");
        typeList.add("wmv");
        //获取文件名和后缀
        String suffix = path.substring(path.lastIndexOf(".") + 1);
        for(String type : typeList) {
            if(type.equalsIgnoreCase(suffix)) {
                return true;
            }
        }
        return false;
    }

    public static BufferedImage resize(BufferedImage img, int newW, int newH) {
        int w = img.getWidth();
        int h = img.getHeight();
        BufferedImage dimg = new BufferedImage(newW, newH, img.getType());
        Graphics2D g = dimg.createGraphics();
        g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
                RenderingHints.VALUE_INTERPOLATION_BILINEAR);
        g.drawImage(img, 0, 0, newW, newH, 0, 0, w, h, null);
        g.dispose();
        return dimg;
    }
}

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