c - C中图像旋转的openCV中心

Question

我想逆时针旋转90度，但是好像旋转点不对。如何找到源图像的旋转中心？

    img=cvLoadImage(argv[1],-1); 
height    = img->height;
width     = img->width;
step      = img->widthStep;
channels  = img->nChannels;
data      = (uchar *)img->imageData;

    IplImage *rotatedImg = cvCreateImage(cvSize(height,width), IPL_DEPTH_8U,img->nChannels);

    CvPoint2D32f center;
    center.x = width/2;
    center.y = height/2;
    CvMat *mapMatrix = cvCreateMat( 2, 3, CV_32FC1 );

    cv2DRotationMatrix(center, 90, 1.0, mapMatrix);
    cvWarpAffine(img, rotatedImg, mapMatrix, CV_INTER_LINEAR + CV_WARP_FILL_OUTLIERS, cvScalarAll(0));


cvShowImage("My image", rotatedImg );

Answer 1

您必须设置仿射变换矩阵的平移参数。

要将图像旋转 90 度并使输出适合目标图像，您可以执行以下操作:

IplImage *rotatedImg = cvCreateImage(cvSize(height,width), IPL_DEPTH_8U,img->nChannels);

CvPoint2D32f center;
center.x = width/2.0f;
center.y = height/2.0f;
CvMat *mapMatrix = cvCreateMat( 2, 3, CV_32FC1 );

float x = width - 1.0f;
float y = 0.0f;

cv2DRotationMatrix(center, 90, 1, mapMatrix);
cvmSet(mapMatrix,0,2,y);
cvmSet(mapMatrix,1,2,x);
cvWarpAffine(img, rotatedImg, mapMatrix, CV_INTER_LINEAR + CV_WARP_FILL_OUTLIERS, cvScalarAll(0));

记下偏移值 x 和 y。这些值根据输出图像大小调整结果。

附言:这不是一个通用的解决方案。仅适用于旋转 90 度。