OpenCV:如何旋转IplImage？

Question

我需要用很小的角度旋转图像，比如1-5度。OpenCV提供了简单的方法吗？通过阅读文档，我可以假设应该涉及到getAffineTransform()，但是没有直接的例子来执行这样的操作：

IplImage *rotateImage( IplImage *source, double angle);

Answer 1

如果您使用OpenCV > 2.0，那么它就像

using namespace cv;

Mat rotateImage(const Mat& source, double angle)
{
    Point2f src_center(source.cols/2.0F, source.rows/2.0F);
    Mat rot_mat = getRotationMatrix2D(src_center, angle, 1.0);
    Mat dst;
    warpAffine(source, dst, rot_mat, source.size());
    return dst;
}

注：角是度，而不是弧度。

有关详细信息，请参阅C++接口文档，并根据需要进行调整：

• getRotationMatrix
• warpAffine

Answer 2

编辑:为了降低投票者:请评论为什么要投票给一个经过测试的代码？

#include "cv.h"
#include "highgui.h"
#include "math.h"
int main( int argc, char** argv )
{
    IplImage* src = cvLoadImage("lena.jpg", 1);    
    IplImage* dst = cvCloneImage( src );

    int delta = 1;
    int angle = 0;
    int opt = 1;   // 1： rotate & zoom
               // 0:  rotate only
    double factor;
    cvNamedWindow("src", 1);
    cvShowImage("src", src);

    for(;;)
    {
    float m[6];
    CvMat M = cvMat(2, 3, CV_32F, m);
    int w = src->width;
    int h = src->height;

    if(opt)  
        factor = (cos(angle*CV_PI/180.) + 1.05) * 2;
    else 
        factor = 1;
    m[0] = (float)(factor*cos(-angle*2*CV_PI/180.));
    m[1] = (float)(factor*sin(-angle*2*CV_PI/180.));
    m[3] = -m[1];
    m[4] = m[0];
    m[2] = w*0.5f;  
    m[5] = h*0.5f;  

    cvGetQuadrangleSubPix( src, dst, &M);
    cvNamedWindow("dst", 1);
    cvShowImage("dst", dst);
    if( cvWaitKey(1) == 27 )
        break;
    angle =(int)(angle + delta) % 360;
    }     
    return 0;
}

UPDATE：参见使用warpaffine cpp.cpp?r=48旋转的代码

#include <cv.h>
#include <highgui.h>

using namespace cv;

int
main(int argc, char **argv)
{
  // (1)load a specified file as a 3-channel color image,
  //    set its ROI, and allocate a destination image
  const string imagename = argc > 1 ? argv[1] : "../image/building.png";
  Mat src_img = imread(imagename);
  if(!src_img.data)
    return -1;
  Mat dst_img = src_img.clone();

  // (2)set ROI
  Rect roi_rect(cvRound(src_img.cols*0.25), cvRound(src_img.rows*0.25), cvRound(src_img.cols*0.5), cvRound(src_img.rows*0.5));
  Mat src_roi(src_img, roi_rect);
  Mat dst_roi(dst_img, roi_rect);

  // (2)With specified three parameters (angle, rotation center, scale)
  //    calculate an affine transformation matrix by cv2DRotationMatrix
  double angle = -45.0, scale = 1.0;
  Point2d center(src_roi.cols*0.5, src_roi.rows*0.5);
  const Mat affine_matrix = getRotationMatrix2D( center, angle, scale );

  // (3)rotate the image by warpAffine taking the affine matrix
  warpAffine(src_roi, dst_roi, affine_matrix, dst_roi.size(), INTER_LINEAR, BORDER_CONSTANT, Scalar::all(255));

  // (4)show source and destination images with a rectangle indicating ROI
  rectangle(src_img, roi_rect.tl(), roi_rect.br(), Scalar(255,0,255), 2);

  namedWindow("src", CV_WINDOW_AUTOSIZE);
  namedWindow("dst", CV_WINDOW_AUTOSIZE);
  imshow("src", src_img);
  imshow("dst", dst_img);
  waitKey(0);

  return 0;
}

Answer 3

看看我对类似问题的答案：

在C/C++中旋转图像

本质上，使用cvWarpAffine -我在前面的答案中描述了如何从这个角度获得2x3变换矩阵。