要从PDF中提取图像及其元数据,可以使用Java的PDF库,如Apache PDFBox或iText。以下是使用Apache PDFBox提取图像及其元数据的示例代码: ```java import java.io.File; import java.io.IOException; import java.util.List; import org.apache.pdfbox.cos.COSDictionary; import org.apache.pdfbox.cos.COSName; import org.apache.pdfbox.pdmodel.PDDocument; import org.apache.pdfbox.pdmodel.PDPage; import org.apache.pdfbox.pdmodel.graphics.image.PDImageXObject; public class PDFImageExtractor { public static void main(String[] args) throws IOException { File file = new File("example.pdf"); PDDocument document = PDDocument.load(file); List<PDPage> pages = document.getPages(); for (PDPage page : pages) { int pageNumber = document.getPageNumber(page); List<PDImageXObject> images = page.getResources().getImages(); for (PDImageXObject image : images) { COSDictionary dictionary = image.getCOSObject(); String subtype = dictionary.getNameAsString(COSName.SUBTYPE); int width = image.getWidth(); int height = image.getHeight(); String colorSpace = image.getColorSpace().getName(); System.out.println("Page " + pageNumber + ": " + subtype + " image, " + width + "x" + height + ", " + colorSpace); } } document.close(); } } ``` 此代码将打印每个页面中的图像类型、大小和颜色空间。可以根据需要修改代码以提取其他元数据。