Java Graphics - 如何加载位图图像并处理单个像素

import java.awt.image.BufferedImage;
import java.io.File;

import javax.imageio.ImageIO;

public class Main {
  public static void main(String[] args) throws Exception {
    BufferedImage img = ImageIO.read(new File("c:/Java_Dev/a.jpg"));
    int height = img.getHeight();
    int width = img.getWidth();

    System.out.println(height + "  " + width + " " + img.getRGB(30, 30));

    for (int h = 1; h < height; h++) {
      for (int w = 1; w < width; w++) {
        int rgb = img.getRGB(w, h);
        int red = (rgb >> 16) & 0x000000FF;
        int green = (rgb >> 8) & 0x000000FF;
        int blue = (rgb) & 0x000000FF;

        if (red == 0 && green == 0 && blue == 0) {
           System.out.println("Black");
        }
      }
    }
  }
}