我使用此代码在OpenCV中旋转我的图像:
// get rotation matrix for rotating the image around its center
Point2f center22(RGBsrc.cols/2.0, RGBsrc.rows/2.0);
Mat rot = getRotationMatrix2D(center22, Angle, 1.0);
// determine bounding rectangle
Rect bbox = RotatedRect(center22,RGBsrc.size(),Angle).boundingRect();
// adjust transformation matrix
rot.at<double>(0,2) += bbox.width/2.0 - center22.x;
rot.at<double>(1,2) += bbox.height/2.0 - center22.y;
Mat dst;
warpAffine(RGBsrc, dst, rot, bbox.size());
imshow("rotated_im", dst);
它工作正常。现在我想将该图像旋转回原始图像。当我使用下面的代码时,我看到图像中对象的位置与原始图像中的位置不同。这是为什么以及如何将图像旋转回来?
Point2f center22(RGBsrc.cols/2.0, RGBsrc.rows/2.0);
Mat rot2 = getRotationMatrix2D(center22, -Angle, 1.0);
Rect bbox2 = RotatedRect(center22,RGBsrc.size(), -Angle).boundingRect();
rot2.at<double>(0,2) += bbox2.width/2.0 - center22.x;
rot2.at<double>(1,2) += bbox2.height/2.0 - center22.y;
Mat Rotatedback;
warpAffine(RotatedRGB, Rotatedback, rot2, bbox2.size());
而不是重新计算变换矩阵,为什么不简单地采用它的逆?
// Invert the affine transformation
Mat rotInv;
cv::invertAffineTransform(rot, rotInv);
您可以像以前一样旋转它:
// get rotation matrix for rotating the image around its center
Point2f center22(RGBsrc.cols / 2.0, RGBsrc.rows / 2.0);
Mat rot = getRotationMatrix2D(center22, Angle, 1.0);
// determine bounding rectangle
Rect bbox = RotatedRect(center22, RGBsrc.size(), Angle).boundingRect();
// adjust transformation matrix
rot.at<double>(0, 2) += bbox.width / 2.0 - center22.x;
rot.at<double>(1, 2) += bbox.height / 2.0 - center22.y;
Mat RotatedRGB;
warpAffine(RGBsrc, RotatedRGB, rot, bbox.size());
然后计算逆变换矩阵并扭曲:
// Invert the affine transformation
Mat rotInv;
cv::invertAffineTransform(rot, rotInv);
// Get back the original image
Mat Rotatedback;
warpAffine(RotatedRGB, Rotatedback, rotInv, Size(RGBsrc.cols, RGBsrc.rows));
完整代码供参考:
#include <opencv2\opencv.hpp>
using namespace cv;
int main()
{
Mat3b RGBsrc = imread("path_to_image");
double Angle = 30.0;
// get rotation matrix for rotating the image around its center
Point2f center22(RGBsrc.cols / 2.0, RGBsrc.rows / 2.0);
Mat rot = getRotationMatrix2D(center22, Angle, 1.0);
// determine bounding rectangle
Rect bbox = RotatedRect(center22, RGBsrc.size(), Angle).boundingRect();
// adjust transformation matrix
rot.at<double>(0, 2) += bbox.width / 2.0 - center22.x;
rot.at<double>(1, 2) += bbox.height / 2.0 - center22.y;
Mat RotatedRGB;
warpAffine(RGBsrc, RotatedRGB, rot, bbox.size());
// Invert the affine transformation
Mat rotInv;
cv::invertAffineTransform(rot, rotInv);
// Get back the original image
Mat Rotatedback;
warpAffine(RotatedRGB, Rotatedback, rotInv, Size(RGBsrc.cols, RGBsrc.rows));
imshow("Original", RGBsrc);
imshow("Rotated", RotatedRGB);
imshow("Rotated Back", Rotatedback);
waitKey();
return 0;
}
如果在调用WARP_INVERSE_MAP
时添加warpAffine()
标志,它将应用逆变换矩阵,让您回到原始图像。例如,您应该能够使用以下内容替换问题中的最后一行代码:
warpAffine(RotatedRGB, Rotatedback, rot, RGBsrc.size(), INTER_LINEAR|WARP_INVERSE_MAP);
注意:我没有测试过这段代码,但是我用WARP_INVERSE_MAP
用warpPerspective()
做了同样的事情,它运行得很好。
文档:https://docs.opencv.org/3.4/da/d54/group__imgproc__transform.html#ga0203d9ee5fcd28d40dbc4a1ea4451983