引入所需依赖，注意poi版本，新版本不支持，最好使用和我一样的版本。

org.apache.poi poi 3.10-FINAL
org.apache.poi poi-ooxml 3.10-FINAL

org.apache.poi poi-ooxml-schemas 3.10-FINAL

org.apache.poi poi-scratchpad 3.10-FINAL

com.github.virtuald curvesapi 1.06

org.apache.xmlbeans xmlbeans 3.1.0

调用方式：
   参数fileformat：文件名后缀，例ppt、pptx
   参数str：文件绝对路径

public static void saveYulanFile(String fileformat,String str) throws Exception {
    if(fileformat.equals("ppt") || fileformat.equals("pptx")){
        PptToImage.createPPTImage(new FileInputStream(new File(str)),str.substring(0,str.indexOf("."))+"/");
    }

}

import org.apache.poi.POIXMLDocument;
import org.apache.poi.hslf.model.Slide;
import org.apache.poi.hslf.model.TextRun;
import org.apache.poi.hslf.usermodel.RichTextRun;
import org.apache.poi.hslf.usermodel.SlideShow;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.apache.poi.xslf.usermodel.XMLSlideShow;
import org.apache.poi.xslf.usermodel.XSLFSlide;
import org.openxmlformats.schemas.drawingml.x2006.main.*;
import org.openxmlformats.schemas.presentationml.x2006.main.CTGroupShape;
import org.openxmlformats.schemas.presentationml.x2006.main.CTShape;
import org.openxmlformats.schemas.presentationml.x2006.main.CTSlide;
import java.awt.*;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.io.*;

/**
* @author ：llf
* @date ：Created in 2020-04-09 11:56
* @description：${description}
* @version: v1.0
*/
public class PptToImage {

public static void create2007PPTImage(InputStream in,String fileOutPath){
    try {
        XMLSlideShow xmlSlideShow=new XMLSlideShow(in);
        Dimension pgsize = xmlSlideShow.getPageSize();
        XSLFSlide\[\] slides = xmlSlideShow.getSlides();
        FileOutputStream out = null;
        for (int i = 0;i < slides.length;i++){
            CTSlide rawSlide=slides\[i\].getXmlObject();
            CTGroupShape gs = rawSlide.getCSld().getSpTree();
            CTShape\[\] shapes = gs.getSpArray();
            for (CTShape shape : shapes) {
                CTTextBody tb = shape.getTxBody();
                if (null == tb)
                    continue;
                CTTextParagraph\[\] paras = tb.getPArray();
                CTTextFont font=CTTextFont.Factory.parse(
                        "<xml-fragment xmlns:a=\\"http://schemas.openxmlformats.org/drawingml/2006/main\\" xmlns:r=\\"http://schemas.openxmlformats.org/officeDocument/2006/relationships\\" xmlns:p=\\"http://schemas.openxmlformats.org/presentationml/2006/main\\">"+
                                "<a:rPr lang=\\"zh-CN\\" altLang=\\"en-US\\" dirty=\\"0\\" smtClean=\\"0\\"> "+
                                "<a:latin typeface=\\"+mj-ea\\"/> "+
                                "</a:rPr>"+
                                "</xml-fragment>");
                for (CTTextParagraph textParagraph : paras) {
                    CTRegularTextRun\[\] textRuns = textParagraph.getRArray();
                    for (CTRegularTextRun textRun : textRuns) {
                        CTTextCharacterProperties properties=textRun.getRPr();
                        properties.setLatin(font);
                    }
                }
            }
            BufferedImage img=new BufferedImage(pgsize.width,pgsize.height, BufferedImage.TYPE\_INT\_RGB);
            Graphics2D graphics=img.createGraphics();
            graphics.setPaint(Color.WHITE);
            graphics.fill(new Rectangle2D.Float(0, 0, pgsize.width,pgsize.height));
            slides\[i\].draw(graphics);
            out = new FileOutputStream(fileOutPath+i+".png");
            javax.imageio.ImageIO.write(img, "png", out);
        }
        out.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

public static void create2003PPTImage(InputStream in,String fileOutPath){
    try {
        SlideShow slideShow=new SlideShow(in);
        Dimension pgsize = slideShow.getPageSize();
        Slide\[\] slides=slideShow.getSlides();
        FileOutputStream out = null;
        for(int i = 0;i < slides.length;i++){
            TextRun\[\] rtruns = slides\[i\].getTextRuns();
            for(TextRun tr: rtruns){
                for (RichTextRun index : tr.getRichTextRuns()){
                    index.setFontName("宋体");
                }
            }
            BufferedImage img=new BufferedImage(pgsize.width,pgsize.height, BufferedImage.TYPE\_INT\_RGB);
            Graphics2D graphics=img.createGraphics();
            graphics.setPaint(Color.WHITE);
            graphics.fill(new Rectangle2D.Float(0, 0, pgsize.width,pgsize.height));
            slides\[i\].draw(graphics);
            out = new FileOutputStream(fileOutPath+i+".png");
            javax.imageio.ImageIO.write(img, "png", out);
        }
        out.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

public static void createPPTImage(InputStream in,String fileOutPath){
    try {
        if(!in.markSupported()){
            in=new BufferedInputStream(in);
        }
        if(in.markSupported()){
            in=new PushbackInputStream(in,8);
        }
        File file = new File(fileOutPath);
        if(!file.exists()){
            file.mkdirs();
        }
        if(POIFSFileSystem.hasPOIFSHeader(in)){//2003
            create2003PPTImage(in,fileOutPath);
        }else if(POIXMLDocument.hasOOXMLHeader(in)){//2007
            create2007PPTImage(in,fileOutPath);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

}

生成的图片目录和文件路径在同一位置