Java Graphics - 如何设置Color作为int值用于setRGB(int x，int y，int rgb)方法？ - Java

import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.awt.image.ColorConvertOp;
import java.io.File;

import javax.imageio.ImageIO;

public class Main {
  public static void main(String[] args) throws Exception{
    int size = 120;
    int pad = 10;
    BufferedImage bi = new BufferedImage(size, size, BufferedImage.TYPE_INT_RGB);
    Graphics g = bi.createGraphics();
    g.setColor(Color.WHITE);
    g.fillRect(0, 0, size, size);
    g.setColor(Color.YELLOW);
    g.fillOval(pad, pad, size - (2 * pad), size - (2 * pad));
    g.dispose();

    BufferedImage image2 = new BufferedImage(bi.getWidth(), bi.getHeight(),
        BufferedImage.TYPE_BYTE_GRAY);

    ColorConvertOp op = new ColorConvertOp(bi.getColorModel().getColorSpace(),
        image2.getColorModel().getColorSpace(), null);
    op.filter(bi, image2);
    ImageIO.write(image2, "png", new File("c:/Java_Dev/image2.png"));
  }
}