java使用Graphics2D压缩图片

要使用Java的Graphics2D类压缩图片，你可以按照以下步骤：

1. 加载要压缩的图片，可以使用ImageIO类：

BufferedImage originalImage = ImageIO.read(new File("path/to/image"));

2. 创建一个新的BufferedImage对象，设置它的宽度和高度为原始图像的一半，或者其他你想要的压缩比例：

int originalWidth = originalImage.getWidth();
int originalHeight = originalImage.getHeight();

int newWidth = originalWidth / 2;  // 压缩一半
int newHeight = originalHeight / 2;  // 压缩一半

BufferedImage compressedImage = new BufferedImage(newWidth, newHeight, originalImage.getType());

3. 获取Graphics2D对象，用它来绘制压缩后的图像：

Graphics2D g2d = compressedImage.createGraphics();
g2d.drawImage(originalImage, 0, 0, newWidth, newHeight, null);
g2d.dispose();

4. 最后，将压缩后的图像保存到文件或输出流中，可以使用ImageIO类：

ImageIO.write(compressedImage, "jpg", new File("path/to/compressed/image.jpg"));

完整的代码：

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

public class ImageCompressor {
    public static void main(String[] args) throws Exception {
        BufferedImage originalImage = ImageIO.read(new File("path/to/image"));

        int originalWidth = originalImage.getWidth();
        int originalHeight = originalImage.getHeight();

        int newWidth = originalWidth / 2;  // 压缩一半
        int newHeight = originalHeight / 2;  // 压缩一半

        BufferedImage compressedImage = new BufferedImage(newWidth, newHeight, originalImage.getType());

        Graphics2D g2d = compressedImage.createGraphics();
        g2d.drawImage(originalImage, 0, 0, newWidth, newHeight, null);
        g2d.dispose();

        ImageIO.write(compressedImage, "jpg", new File("path/to/compressed/image.jpg"));
    }
}