我正在使用Apache POI将PPTX幻灯片转换为图像，但生成的图像非常大，超过1.5mb

Question

我已经通过一些在线工具转换了相同的pptx文件，为幻灯片生成的图像比通过POI生成的图像要少得多。

try {
        //creating an empty presentation
        //File file = new File("/Users/dk/Documents/Jitendra/work/Rough/download_images/pptx1.pptx");
        XMLSlideShow ppt = new XMLSlideShow(new FileInputStream("lighthouse_tobeused.pptx"));

        //getting the dimensions and size of the slide
        Dimension pgsize = ppt.getPageSize();
        List<XSLFSlide> slide = ppt.getSlides();

        BufferedImage img = null;

        int imgWidth = pgsize.width;
        int imgHeight = pgsize.height;

        for (int i = 0; i < slide.size(); i++) {
            LOG.info("imgWidth => "+imgWidth+" ,imgHeight => "+imgHeight);

            img = new BufferedImage(imgWidth, imgHeight, BufferedImage.TYPE_INT_RGB);
            Graphics2D graphics = img.createGraphics();

            graphics.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            graphics.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
            graphics.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
            graphics.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);

            graphics.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
            graphics.setRenderingHint(RenderingHints.KEY_TEXT_LCD_CONTRAST, 150);


            graphics.setColor(Color.white);
            graphics.clearRect(0, 0, imgWidth, imgHeight);
            graphics.fill(new Rectangle2D.Float(0, 0, imgWidth, imgHeight));

            //render
            slide.get(i).draw(graphics);

           FileOutputStream out = new FileOutputStream("ppt_image_"+i+".jpg");
            javax.imageio.ImageIO.write(img, "jpg", out);
            ppt.write(out);
            //LOG.info("Image successfully created");
            out.close();

Answer 1

首先，从您的代码中删除ppt.write(out);。它将整个XMLSlideShow ppt写入到每个FileOutputStream out的ppt_image_*.jpg中。这是没有用的，只会给每个ppt_image_*.jpg文件添加不必要的字节。

如果大小不够小，您可以使用java.awt.geom.AffineTransform设置缩放比例因子，然后将该转换设置为使用的Graphics2D。

...
Double zoom = .5d;
AffineTransform at = new AffineTransform();
at.setToScale(zoom, zoom);
...
Graphics2D graphics = img.createGraphics();
graphics.setTransform(at);
...

小于1d的缩放因子将导致较小的图像大小，因此文件大小也较小。

完整示例：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics2D;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.awt.geom.AffineTransform;
import java.awt.RenderingHints;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import javax.imageio.ImageIO;

import org.apache.poi.xslf.usermodel.XMLSlideShow;
import org.apache.poi.xslf.usermodel.XSLFSlide;

public class PptToImage {

   public static void main(String args[]) throws Exception {

      FileInputStream in =new FileInputStream("PPTX.pptx");
      XMLSlideShow ppt = new XMLSlideShow(in);

      //set zoom factor
      Double zoom = .5d;
      AffineTransform at = new AffineTransform();
      at.setToScale(zoom, zoom);

      //get the dimension of size of the slide 
      Dimension pgsize = ppt.getPageSize();

      //get slides 
      java.util.List<XSLFSlide> slides = ppt.getSlides();

      BufferedImage img = null;
      FileOutputStream out = null;

      for (int i = 0; i < slides.size(); i++) {
         img = new BufferedImage((int)Math.ceil(pgsize.width * zoom), (int)Math.ceil(pgsize.height * zoom), BufferedImage.TYPE_INT_RGB);
         Graphics2D graphics = img.createGraphics();

         //set scaling transform
         graphics.setTransform(at);

         graphics.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
         graphics.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
         graphics.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
         graphics.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);

         graphics.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
         graphics.setRenderingHint(RenderingHints.KEY_TEXT_LCD_CONTRAST, 150);

         //clear the drawing area
         graphics.setPaint(Color.white);
         graphics.fill(new Rectangle2D.Float(0, 0, pgsize.width, pgsize.height));

         //render
         slides.get(i).draw(graphics);

         //creating an image file as output
         out = new FileOutputStream("ppt_image_" + i + ".png");
         ImageIO.write(img, "png", out);
         out.close();   
      }
   }
}

玩不同的Double zoom = .5d;