pdfbox如何裁剪pdf

使用 Apache PDFBox 可以很方便地裁剪 PDF。以下是一个示例程序，演示如何使用 PDFBox 裁剪 PDF：

import java.io.File;
import java.io.IOException;
import org.apache.pdfbox.cos.COSArray;
import org.apache.pdfbox.cos.COSDictionary;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.multipdf.PDFMergerUtility;
import org.apache.pdfbox.pdfparser.PDFParser;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.common.PDRectangle;
import org.apache.pdfbox.pdmodel.graphics.color.PDColor;
import org.apache.pdfbox.pdmodel.graphics.color.PDDeviceRGB;
import org.apache.pdfbox.pdmodel.graphics.state.PDExtendedGraphicsState;
import org.apache.pdfbox.pdmodel.graphics.state.PDGraphicsState;
import org.apache.pdfbox.pdmodel.interactive.documentnavigation.destination.PDPageFitWidthDestination;
import org.apache.pdfbox.pdmodel.interactive.documentnavigation.destination.PDPageXYZDestination;
import org.apache.pdfbox.util.Matrix;

public class PdfCropper {

    public static void main(String[] args) throws IOException {
        String inputFileName = "input.pdf";
        String outputFileName = "output.pdf";

        // Create a PDF parser and parse the input file
        PDFParser parser = new PDFParser(new File(inputFileName));
        parser.parse();

        // Load the parsed document
        PDDocument document = parser.getPDDocument();

        // Get the first page of the document
        PDPage page = document.getPage(0);

        // Set the crop box to be a smaller rectangle
        PDRectangle cropBox = new PDRectangle(72, 72, 468, 648);
        page.setCropBox(cropBox);

        // Set the media box to be the same as the crop box
        PDRectangle mediaBox = new PDRectangle(cropBox.getWidth(), cropBox.getHeight());
        page.setMediaBox(mediaBox);

        // Set the page display mode to fit the width of the screen
        PDPageFitWidthDestination fitWidth = new PDPageFitWidthDestination();
        fitWidth.setPageNumber(0);
        page.setDisplayMode(PDPageFitWidthDestination.DISPLAY_MODE_FIT_WIDTH);

        // Set the page zoom to 100%
        PDPageXYZDestination xyz = new PDPageXYZDestination();
        xyz.setPageNumber(0);
        xyz.setZoom(1.0f);
        page.setCurrentZoom(1.0f);

        // Set the page background color to white
        PDColor white = new PDColor(new float[]{1, 1, 1}, PDDeviceRGB.INSTANCE);
        PDExtendedGraphicsState graphicsState = new PDExtendedGraphicsState();
        graphicsState.setNonStrokingColor(white);
        PDGraphicsState state = new PDGraphicsState();
        state.setNonStrokingColorSpace(PDDeviceRGB.INSTANCE);
        state.setNonStrokingColor(white);
        state.setStrokingColorSpace(PDDeviceRGB.INSTANCE);
        state.setStrokingColor(white);
        page.setGraphicsStateParameters(state, graphicsState);

        // Save the modified document
        document.save(outputFileName);

        // Close the document
        document.close();
    }

}

此示例程序使用 `setCropBox()` 方法将 PDF 的裁剪框设置为 `(72, 72, 468, 648)`，这意味着裁剪框的左下角在 `(72, 72)`，右上角在 `(72+468, 72+648)`。然后使用 `setMediaBox()` 方法将媒体框设置为与裁剪框相同的大小。页面显示模式设置为适合屏幕宽度，页面缩放设置为 100%，页面背景色设置为白色。最后，使用 `save()` 方法保存修改后的文档。