自适应长宽，并且背景和 excel单元格背景一致

要实现自适应长宽且背景和Excel单元格一致的转换，你可以使用以下代码：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class ExcelToImageConverter {
    public static void main(String[] args) throws Exception {
        // Load Excel file
        Workbook workbook = new XSSFWorkbook(new FileInputStream("input.xlsx"));

        // Get first sheet
        Sheet sheet = workbook.getSheetAt(0);

        // Get sheet dimensions
        int rows = sheet.getLastRowNum() + 1;
        int cols = sheet.getRow(0).getLastCellNum();

        // Create image buffer
        int cellWidth = 100;
        int cellHeight = 25;
        int width = cols * cellWidth;
        int height = rows * cellHeight;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2 = image.createGraphics();
        g2.setColor(Color.WHITE);
        g2.fillRect(0, 0, width, height);

        // Draw Excel cells onto image buffer
        for (int r = 0; r < rows; r++) {
            Row row = sheet.getRow(r);
            for (int c = 0; c < cols; c++) {
                Cell cell = row.getCell(c);
                if (cell != null) {
                    Rectangle cellRect = new Rectangle(c * cellWidth, r * cellHeight, cellWidth, cellHeight);
                    g2.setColor(getCellColor(cell));
                    g2.fill(cellRect);
                    g2.setColor(Color.BLACK);
                    g2.draw(cellRect);
                    String value = cell.toString();
                    g2.drawString(value, cellRect.x + 5, cellRect.y + 15);
                }
            }
        }
        g2.dispose();

        // Save image to file
        ImageIO.write(image, "png", new FileOutputStream("output.png"));

        // Close workbook
        workbook.close();
    }

    private static Color getCellColor(Cell cell) {
        Color color = Color.WHITE;
        if (cell.getCellStyle() != null) {
            short fgColorIndex = cell.getCellStyle().getFillForegroundColor();
            color = cell.getSheet().getWorkbook().getCustomPalette().getColor(fgColorIndex);
        }
        return color;
    }
}

这个例子将Excel文件转换为PNG图像，并将其保存到文件中。生成的图像将根据单元格的数量自适应调整大小，并将单元格的背景色应用到图像中。注意，这里的代码假设每个单元格都是正方形的。如果你的Excel文件中的单元格不是正方形，你需要修改代码来适应不同的单元格大小。