使用pdfbox将pdf文件转换为java中的图像时缺少文本

我想将PDF页面转换为图像文件.当我使用Java将PDF页面转换为图像时，缺少文本.

I want to convert a PDF page to image file. Text is missing when I convert a PDF page to image using java.

我要转换的文件 46_2.pdf 转换后显示为 46_2.png

The file which I want to convert 46_2.pdf after converting it shown me like 46_2.png

代码:

import java.awt.image.BufferedImage;
import java.io.File;
import java.util.List;

import javax.imageio.ImageIO;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;

public class ConvertPDFPageToImageWithoutText {
    public static void main(String[] args) {
        try {
            String oldPath = "C:/PDFCopy/46_2.pdf";
            File oldFile = new File(oldPath);
           if (oldFile.exists()) {

            PDDocument document = PDDocument.load(oldPath);
            List<PDPage> list = document.getDocumentCatalog().getAllPages();

            for (PDPage page : list) {
                BufferedImage image = page.convertToImage();
                File outputfile = new File("C:/PDFCopy/image.png");
                ImageIO.write(image, "png", outputfile);
                document.close();
            }

        }

    } catch (Exception e) {
        e.printStackTrace();
    }
}
}