如何在java中缩放图像？我需要的是算法而不是预定义函数

import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;

public class ImageScaler {
    public static void main(String[] args) {
        try {
            // 读取原始图像
            BufferedImage originalImage = ImageIO.read(new File("original.jpg"));
            
            // 指定缩放后的宽度和高度
            int scaledWidth = 200;
            int scaledHeight = 200;
            
            // 创建新的图像对象
            BufferedImage scaledImage = new BufferedImage(scaledWidth, scaledHeight, BufferedImage.TYPE_INT_RGB);
            
            // 使用Graphics2D对象进行缩放
            Graphics2D g2d = scaledImage.createGraphics();
            g2d.drawImage(originalImage, 0, 0, scaledWidth, scaledHeight, null);
            g2d.dispose();
            
            // 保存缩放后的图像
            ImageIO.write(scaledImage, "jpg", new File("scaled.jpg"));
            
            System.out.println("图像缩放成功！");
        } catch (IOException e) {
            System.out.println("图像缩放失败：" + e.getMessage());
        }
    }
}