直接上代碼：

package com.henu.test;

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

public class ImgTest {

    public static void createImgThumbnail(String imgSrc, int thumbWidth,
            int thumbHeight, String outFilePath) throws
 
 InterruptedException,
            IOException {
        File imageFile = new File(imgSrc);
        BufferedImage image = ImageIO.read(imageFile);
        Integer width = image.getWidth();
        Integer height = image.getHeight();
        double i = (double) width / (double) height;
        double j = (double
 
) thumbWidth / (double) thumbHeight;
        int[] d = new int[2];
        int x = 0;
        int y = 0;
        if (i > j) {
            d[1] = thumbHeight;
            d[0] = (int) (thumbHeight * i);
            y = 0;
            x = (d[0] - thumbWidth) / 2;
        } else {
            d[0] = thumbWidth;
            d[
 
1] = (int) (thumbWidth / i);
            x = 0;
            y = (d[1] - thumbHeight) / 2;
        }
        File outFile = new File(outFilePath);
        if (!outFile.getParentFile().exists()) {
            outFile.getParentFile().mkdirs();
        }

        /* 等比例縮放 */
        BufferedImage newImage = new BufferedImage(d[0], d[1], image.getType());
        Graphics g = newImage.getGraphics();
        g.drawImage(image, 0, 0, d[0], d[1], null);
        g.dispose();
        /* 居中剪裁 */
        newImage = newImage.getSubimage(x, y, thumbWidth, thumbHeight);
        ImageIO.write(
                newImage,
                imageFile.getName().substring(
                        imageFile.getName().lastIndexOf(".") + 1), outFile);
    }

    public static void main(String[] args) throws Exception {
        ImgTest.createImgThumbnail("D:/test/2.jpg", 510, 288, 
                "D:/test/test_2.jpg");
    }
}

自定義高度寬度縮小圖片