Base64字符串图片旋转工具类

public class Base64ToPhotoUtil {

    /**
     * base64签名图片旋转
     *
     * @param base64
     * @return
     */
    public static String rotate(String base64) {
        String value = base64;
        try {
            byte[] bytes = Base64.decodeBase64(base64.substring(base64.indexOf(",")));
            InputStream is = new ByteArrayInputStream(bytes);
            BufferedImage image = ImageIO.read(is);
            if (image.getHeight() > image.getWidth()) {
                Color bgColor = new Color(255, 255, 255);
                BufferedImage result = rotateImage(image, 90, bgColor);
                value = BufferedImageToBase64(result);
            }
        } catch (Exception e) {
            throw new RuntimeException("base64图片旋转异常");
        }
        return value;
    }

    /**
     * 创建任意角度的旋转图像
     *
     * @param image
     * @param theta 大于0向右 小于0向左
     * @param backgroundColor
     * @return
     */
    private static BufferedImage rotateImage(BufferedImage image, double theta, Color backgroundColor) {
        int width = image.getWidth();
        int height = image.getHeight();
        double angle = theta * Math.PI / 180; // 度转弧度
        double[] xCoords = getX(width / 2, height / 2, angle);
        double[] yCoords = getY(width / 2, height / 2, angle);
        int WIDTH = (int) (xCoords[3] - xCoords[0]);
        int HEIGHT = (int) (yCoords[3] - yCoords[0]);
        BufferedImage resultImage = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_ARGB);
        for (int i = 0; i < WIDTH; i++) {
            for (int j = 0; j < HEIGHT; j++) {
                int x = i - WIDTH / 2;
                int y = HEIGHT / 2 - j;
                double radius = Math.sqrt(x * x + y * y);
                double angle1;
                if (y > 0) {
                    angle1 = Math.acos(x / radius);
                } else {
                    angle1 = 2 * Math.PI - Math.acos(x / radius);
                }
                x = (int) (radius * Math.cos(angle1 - angle));
                y = (int) (radius * Math.sin(angle1 - angle));
                if (x < (width / 2) & x > -(width / 2) & y < (height / 2) & y > -(height / 2)) {
                    int rgb = image.getRGB(x + width / 2, height / 2 - y);
                    resultImage.setRGB(i, j, rgb);
                } else {
                    int rgb = ((0 & 0xff) << 24) | ((backgroundColor.getRed() & 0xff) << 16) | ((backgroundColor.getGreen() & 0xff) << 8)
                            | ((backgroundColor.getBlue() & 0xff));
                    resultImage.setRGB(i, j, rgb);
                }
            }
        }
        return resultImage;
    }

    // 获取四个角点旋转后Y方向坐标
    private static double[] getY(int i, int j, double angle) {
        double[] results = new double[4];
        double radius = Math.sqrt(i * i + j * j);
        double angle1 = Math.asin(j / radius);
        results[0] = radius * Math.sin(angle1 + angle);
        results[1] = radius * Math.sin(Math.PI - angle1 + angle);
        results[2] = -results[0];
        results[3] = -results[1];
        Arrays.sort(results);
        return results;
    }

    // 获取四个角点旋转后X方向坐标
    private static double[] getX(int i, int j, double angle) {
        double[] results = new double[4];
        double radius = Math.sqrt(i * i + j * j);
        double angle1 = Math.acos(i / radius);
        results[0] = radius * Math.cos(angle1 + angle);
        results[1] = radius * Math.cos(Math.PI - angle1 + angle);
        results[2] = -results[0];
        results[3] = -results[1];
        Arrays.sort(results);
        return results;
    }

    /**
     * BufferedImage 编码转换为 base64
     *
     * @param bufferedImage
     * @return
     */
    private static String BufferedImageToBase64(BufferedImage bufferedImage) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();//io流
        try {
            ImageIO.write(bufferedImage, "png", baos);//写入流中
        } catch (IOException e) {
            e.printStackTrace();
        }
        byte[] bytes = baos.toByteArray();//转换成字节
        String png_base64 = Base64.encodeBase64String(bytes).trim();
        return "data:image/jpg;base64," + png_base64;
    }
}