java 使用itext7将PDF转换为tiff 要求生成一个tiff文件包含多页图像

可以使用以下代码将PDF转换为多页TIFF：

import com.itextpdf.io.source.RandomAccessSourceFactory;
import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfReader;
import com.itextpdf.kernel.pdf.canvas.parser.listener.ITextExtractionStrategy;
import com.itextpdf.kernel.pdf.canvas.parser.PdfCanvasProcessor;
import com.itextpdf.kernel.pdf.canvas.parser.listener.LocationTextExtractionStrategy;
import com.itextpdf.kernel.pdf.canvas.parser.listener.RenderListener;
import com.itextpdf.kernel.pdf.canvas.parser.PdfTextExtractor;
import com.itextpdf.kernel.geom.PageSize;
import com.itextpdf.kernel.geom.Rectangle;
import com.itextpdf.kernel.pdf.canvas.PdfCanvas;
import com.itextpdf.layout.Document;
import com.itextpdf.layout.element.Image;
import com.itextpdf.layout.element.Paragraph;
import com.itextpdf.layout.property.Property;
import com.itextpdf.layout.property.TextAlignment;
import com.itextpdf.text.pdf.RandomAccessFileOrArray;
import com.itextpdf.text.pdf.codec.TIFFEncodeParam;
import com.itextpdf.text.pdf.codec.TiffWriter;

import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import javax.imageio.ImageIO;

public class PdfToTiffConverter {
    public static void main(String[] args) {
        String pdfPath = "path/to/pdf";
        String tiffPath = "path/to/tiff";
        
        try {
            PdfDocument pdfDocument = new PdfDocument(new PdfReader(pdfPath));
            int pageCount = pdfDocument.getNumberOfPages();
            Document document = new Document(pdfDocument.getDefaultPageSize(), 0, true);
            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
            TiffWriter tiffWriter = new TiffWriter(new RandomAccessFileOrArray(outputStream), true);
            TIFFEncodeParam param = new TIFFEncodeParam();
            param.setCompression(TIFFEncodeParam.COMPRESSION_GROUP4);
            
            for (int i = 1; i <= pageCount; i++) {
                PdfCanvas pdfCanvas = new PdfCanvas(pdfDocument.getPage(i));
                BufferedImage bufferedImage = new BufferedImage((int) pdfDocument.getDefaultPageSize().getWidth(), (int) pdfDocument.getDefaultPageSize().getHeight(), BufferedImage.TYPE_INT_RGB);
                pdfCanvas.paint(bufferedImage.createGraphics());
                Image image = new Image(ImageDataFactory.create(bufferedImage, null));
                document.add(image.setAutoScale(true));
                document.add(new Paragraph("").add(new Text(i + "/" + pageCount)).setTextAlignment(TextAlignment.RIGHT).setProperty(Property.FONT_SIZE, 8));
                document.newPage();
                
                TiffWriter.FieldImageData fieldImageData = new TiffWriter.FieldImageData();
                fieldImageData.image = bufferedImage;
                fieldImageData.index = i - 1;
                tiffWriter.addFieldImageData(fieldImageData);
            }
            
            tiffWriter.close();
            outputStream.close();
            byte[] tiffBytes = outputStream.toByteArray();
            FileOutputStream outputStream1 = new FileOutputStream(tiffPath);
            outputStream1.write(tiffBytes);
            outputStream1.close();
            document.close();
            pdfDocument.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

这个代码使用 iText7 库将 PDF 文件转换为多页 TIFF 文件。要使用此代码，需要将 iText7 的 jar 文件添加到您的项目中。在代码中，我们使用 `PdfCanvas` 从 PDF 页面中提取图像，并使用 `Image` 将其添加到 iText 的 `Document` 中。我们还使用 `TiffWriter` 将所有图像写入单个 TIFF 文件中。