现在数码相机拍摄图片都有拍摄方向，水平、垂直拍摄，拍摄后，图像内容会保存相应的信息，我们可以获取这些信息，对图像做展示，不然你会发现，一张图片，90度拍摄后，QImage加载会发生90度旋转，我测试如果不做处理，html5的image标签，python的CV2模块加载图片，都会发现图片方向被旋转90度。再Qt中 可以用如下方式来修正图像方向
代码：

QImageReader reader(path);
reader.setAutoTransform(true);
const QImage newImage = reader.read();
QImageIOHandler::Transformations transformation;
if (newImage.isNull()){QMessageBox::information(nullptr, QGuiApplication::applicationDisplayName(),tr("Cannot load %1: %2").arg(QDir::toNativeSeparators(path), reader.errorString()));return;
}
else {transformation = reader.transformation();qDebug() << "transformation is " << transformation;
} 
if (transformation == QImageIOHandler::TransformationRotate90|| transformation == QImageIOHandler::TransformationMirrorAndRotate90|| transformation == QImageIOHandler::TransformationFlipAndRotate90|| transformation == QImageIOHandler::TransformationRotate270)
{QTransform matrix;matrix.rotate(90);m_pixmap = m_pixmap.transformed(matrix);m_image = m_image.transformed(matrix);
}
else if (transformation == QImageIOHandler::TransformationRotate180)
{QTransform matrix;matrix.rotate(180);m_pixmap = m_pixmap.transformed(matrix);m_image = m_image.transformed(matrix);
}