重点内容
(一) How to read an image from file or URL？

1. 从本地文本读取图片

File sourceimage = new File("c:\\mypic.jpg");
Image image = ImageIO.read(sourceimage);

1. 从网络上获取图片

URL url = new URL("http://www.mkyong.com/image/mypic.jpg");
Image image = ImageIO.read(url);

3.使用ImageIO读取图片实例

package ImageIO;
import java.awt.Image;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;public class ReadImage
{public static void main( String[] args ){Image image = null;try {URL url = new URL("http://img04.tooopen.com/images/20130805/tooopen_10473021.jpg");image = ImageIO.read(url);} catch (IOException e) {e.printStackTrace();}JFrame frame = new JFrame();frame.setSize(300, 300);JLabel label = new JLabel(new ImageIcon(image));frame.add(label);frame.setVisible(true);}
}

结果：

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(二)How to write an image to file - Java ImageIO？

1.ImageIO可以从本地文件中读取图片和写入图片，也可以从网络上读取图片写入本地文件中。

2.演示ImageIO读取URL资源

package ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;public class WriteImage
{public static void main( String[] args ){BufferedImage image = null;try {URL url = new URL("http://p3.so.qhmsg.com/t014d3503dd2d67d728.jpg");image = ImageIO.read(url);//.jpg文件占空间最小ImageIO.write(image, "jpg",new File("D:\\out.jpg"));ImageIO.write(image, "gif",new File("D:\\out.gif"));ImageIO.write(image, "png",new File("D:\\out.png"));} catch (IOException e) {e.printStackTrace();}System.out.println("成功写入D盘");}
}

3.How to load and write an image in Java?

加载图片：

BufferedImage originalImage = ImageIO.read(new File("c:\\image\\1.jpg"));

写入图片：

ImageIO.write(originalImage, "jpg", new File("c:\\image\\1.jpg"));

读写操作实例代码演示：

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;public class ImageTest {public static void main(String[] args) {try {//使用jpg格式，可以减少存储空间BufferedImage originalImage = ImageIO.read(new File("c:\\image\\1.jpg"));ImageIO.write(originalImage, "jpg", new File("c:\\image\\1.jpg"));} catch (IOException e) {System.out.println(e.getMessage());}}}