根据图片缩放

public class Demo {
    public static void main(String[] args) {
        try {
            BufferedImage image = ImageIO.read(new File("G:\\1.png"));
            int width = image.getWidth();
            int height = image.getHeight();
            image.flush();
            System.out.println("Width : " + width);
            System.out.println("Height : " + height);
            Thumbnails.of("G:\\1.png").size(900,900).keepAspectRatio(false).toFile("G:\\2.png");
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

  <dependency>
         <groupId>net.coobird</groupId>
         <artifactId>thumbnailator</artifactId>
         <version>0.4.8</version>
   </dependency>