Opencv image rotation

One 、 Image rotation

operator ：transpose(src, src);

transpose() Pixel subscript can be realized x and y Adjust the axis coordinates ：dst(i,j)=src(j,i), Interface form

transpose(
  InputArray src, //  The input image 
  OutputArray dst, //  Output 
)

operator ：flip(src, src, 1);

flip() Function to flip the image horizontally 、 Flip vertically and flip Bi directionally

void flip(
     InputArray src, //  The input image 
     OutputArray dst, //  Output 
     int flipCode = 0 // >0:  Along the y- The axis turns , 0:  Along the x- The axis turns , <0: x、y The axis turns at the same time 
  );

flip(img1,0)# Flip the horizontal axis （ Flip up and down ）
flip(img1,1)# Flip the vertical axis （ Flip left and right ）
flip(img1,-1)# Flip both ways 

Two 、 Code shows

#if 1  //  Rotation Angle 
Mat rotate_img(Mat src, int idx) {
	// rotate 90 degree 
	if (idx == 1) {
		transpose(src, src);
		flip(src, src, 1);
		return src;
	}
	// rotate 180 degree 
	else if (idx == 2) {
		flip(src, src, 0);
		flip(src, src, 1);
		return src;
	}
	// rotate 270 degree 
	else if (idx == 3) {
		transpose(src, src);
		flip(src, src, 0);
		return src;
	}
	else {
		return src;
	}

}
int main() {
	Mat src = imread("C:\\Users\\19473\\Desktop\\opencv_images\\33.jpg");
	if (!src.data)
	{
		printf("could not  load  image....\n");
	}

	imshow(" Original picture ", src);

	Mat  m1= rotate_img(src,1); //90 degree 
	imshow("90 degree ", m1);
	Mat  m2 = rotate_img(src, 2); //180 degree 
	imshow("180 degree ", m2);
	Mat  m3 = rotate_img(src, 3); //270 degree 
	imshow("270 degree ", m3);
	waitKey(0);
	return 0;
}
#endif