Java: convert PDF to image using ghost4j

问题

I am trying to use the ghost4j library to convert a pdf to image. My code looks like this:

import org.ghost4j.document.*;
import org.ghost4j.renderer.*;
import java.util.ArrayList;
import java.util.List;
.
.
.

        PDFDocument document = new PDFDocument();
        document.load(new File("M:\\test.pdf"));
        SimpleRenderer renderer = new SimpleRenderer();
        renderer.setResolution(300);
        List<Image> images = renderer.render(document);

but I get the following error:

error: cannot find symbol List images = renderer.render(document); ^ symbol: class Image location: class ImageRead 1 error

which indicates that compiler cannot find symbol "Image". I'm not sure why?

来源：https://stackoverflow.com/questions/61872881/java-convert-pdf-to-image-using-ghost4j