java - 将旋转角度的图片旋转回去 -【解决生成缩略图导致图片旋转问题】

获取旋转角度，参考这篇随笔

java - 检查是否有旋转角度导致ImageIO获取宽高相反 - 岑惜 - 博客园 (cnblogs.com)

旋转回去，工具类

import java.awt.*;
import java.awt.image.BufferedImage;

public class RotateImageUtil {

    /**
     * 对图片进行旋转
     *
     * @param src   被旋转图片
     * @param angel 旋转角度
     * @return 旋转后的图片
     */
    public static BufferedImage Rotate(Image src, int angel) {
        int srcWidth = src.getWidth(null);
        int srcHeight = src.getHeight(null);
        // 计算旋转后图片的尺寸
        Rectangle rect_des = CalcRotatedSize(new Rectangle(new Dimension(
                srcWidth, srcHeight)), angel);
        BufferedImage res = null;
        res = new BufferedImage(rect_des.width, rect_des.height,
                BufferedImage.TYPE_INT_RGB);
        Graphics2D g2 = res.createGraphics();
        // 进行转换
        g2.translate((rect_des.width - srcWidth) / 2,
                (rect_des.height - srcHeight) / 2);
        g2.rotate(Math.toRadians(angel), (double) srcWidth / 2, (double) srcHeight / 2);
        g2.drawImage(src, null, null);
        return res;
    }

    /**
     * 计算旋转后的图片
     *
     * @param src   被旋转的图片
     * @param angel 旋转角度
     * @return 旋转后的图片
     */
    private static Rectangle CalcRotatedSize(Rectangle src, int angel) {
        // 如果旋转的角度大于90度做相应的转换
        if (angel >= 90) {
            if (angel / 90 % 2 == 1) {
                int temp = src.height;
                src.height = src.width;
                src.width = temp;
            }
            angel = angel % 90;
        }
        double r = Math.sqrt(src.height * src.height + src.width * src.width) / 2;
        double len = 2 * Math.sin(Math.toRadians(angel) / 2) * r;
        double angelAlpha = (Math.PI - Math.toRadians(angel)) / 2;
        double angelDeltaWidth = Math.atan((double) src.height / src.width);
        double angelDeltaHeight = Math.atan((double) src.width / src.height);
        int lenDeltaWidth = (int) (len * Math.cos(Math.PI - angelAlpha
                - angelDeltaWidth));
        int lenDeltaHeight = (int) (len * Math.cos(Math.PI - angelAlpha
                - angelDeltaHeight));
        int desWidth = src.width + lenDeltaWidth * 2;
        int desHeight = src.height + lenDeltaHeight * 2;
        return new Rectangle(new Dimension(desWidth, desHeight));
    }
}

使用方法

 BufferedImage  继承了 Image  因此可以使用父类