如何在iText7中对圆角表格单元格应用背景色？

import com.itextpdf.kernel.pdf.canvas.PdfCanvas;
import com.itextpdf.layout.element.Cell;
import com.itextpdf.layout.renderer.CellRenderer;

public class RoundedCornerCellRenderer extends CellRenderer {
    public RoundedCornerCellRenderer(Cell modelElement) {
        super(modelElement);
    }

    @Override
    public void draw(DrawContext drawContext) {
        super.draw(drawContext);
        PdfCanvas canvas = drawContext.getCanvas();
        float x = getOccupiedAreaBBox().getX();
        float y = getOccupiedAreaBBox().getY();
        float width = getOccupiedAreaBBox().getWidth();
        float height = getOccupiedAreaBBox().getHeight();
        float radius = 5f; // 圆角半径
        canvas.roundRectangle(x, y, width, height, radius).fill();
    }
}

import com.itextpdf.layout.element.Cell;
import com.itextpdf.layout.renderer.CellRenderer;
import com.itextpdf.layout.renderer.TableRenderer;

public class RoundedCornerTableRenderer extends TableRenderer {
    public RoundedCornerTableRenderer(Table modelElement) {
        super(modelElement);
    }

    @Override
    protected CellRenderer createCellRenderer(Cell modelElement) {
        return new RoundedCornerCellRenderer(modelElement);
    }
}

import com.itextpdf.kernel.pdf.PdfWriter;
import com.itextpdf.layout.Document;
import com.itextpdf.layout.element.Cell;
import com.itextpdf.layout.element.Table;
import com.itextpdf.layout.property.HorizontalAlignment;
import com.itextpdf.layout.property.TextAlignment;

public class RoundedCornerTableExample {
    public static void main(String[] args) {
        try {
            // 创建PDF文档
            PdfWriter writer = new PdfWriter("rounded_corner_table.pdf");
            Document document = new Document(writer);

            // 创建表格
            Table table = new Table(3);
            table.setWidthPercent(100);
            table.setHorizontalAlignment(HorizontalAlignment.CENTER);

            // 添加单元格
            Cell cell1 = new Cell().add("Cell 1");
            Cell cell2 = new Cell().add("Cell 2");
            Cell cell3 = new Cell().add("Cell 3");

            // 设置单元格样式
            cell1.setTextAlignment(TextAlignment.CENTER);
            cell2.setTextAlignment(TextAlignment.CENTER);
            cell3.setTextAlignment(TextAlignment.CENTER);

            // 添加单元格到表格
            table.addCell(cell1);
            table.addCell(cell2);
            table.addCell(cell3);

            // 设置表格渲染器
            table.setNextRenderer(new RoundedCornerTableRenderer(table));

            // 添加表格到文档
            document.add(table);

            // 关闭文档
            document.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}