OpenCV warpAffine相对于任意点旋转

I'm using OpenCV in C++. I have two images of faces, and I'm trying to align the faces to each other. I have features denoting the eyes, nose, and other points of interest in the faces. I use Arun's method to extract a rotation, translation, and scale that translates the centroid of the feature sets in one image to the other. Then, it rotates and scales it. And I'm trying to use this transformation to warp one image so that the face in the image aligns with the face in the other image. At least that's the idea, but I'm having problems. It seems that the rotation and translation are being performed in a different order than I expected in warpAffine. There also seems to be an issue with row/column ordering versus x/y coordinates. Also, as the title suggests, I think the warpAffine is doing the operations with respect to 0,0 in the image whereas I expect them to be done around the centroid of the face points. What should I be doing to correctly align these two sets of points? Here's my code:

我在C ++中使用OpenCV。我有两张脸的图像,我正试图将脸对齐。我有表示眼睛,鼻子和脸上其他兴趣点的特征。我使用Arun的方法来提取旋转,平移和缩放,将一个图像中的特征集的质心转换为另一个图像。然后,它旋转并缩放它。我正在尝试使用此变换来扭曲一个图像,以使图像中的面部与另一个图像中的面部对齐。至少这是个主意,但我遇到了问题。似乎旋转和平移的执行顺序与warpAffine中预期的顺序不同。行/列排序与x / y坐标似乎也存在问题。另外,正如标题所示,我认为warpAffine正在对图像中的0,0进行操作,而我希望它们可以围绕面部点的质心进行。我应该怎么做才能正确对齐这两组点?这是我的代码:

// R is the rotation as computed by Arun's method
// centered_moving is the moving points with the centroid subtracted from them
// same with centered_base
for (int i = 0; i < base.cols; i++)
{
    a = centered_base.col(i);
    b = centered_moving.col(i).t();
    H += a*b;
}
SVD sv;
Mat W, U, Vt;
sv.compute(H, W, U, Vt);
Mat R = (Vt.t())*(U.t());
// centroid_moving and centroid_base are the centroids of the two point clouds, moving is the cloud that will be translated
Mat trans = -centroid_moving + centroid_base;
Mat Afmat = Mat::zeros(2, 3, ddepth);
Mat tmpmat = Afmat(Rect(0, 0, 2, 2));
R = Mat::eye(2, 2, ddepth);
R.copyTo(tmpmat);
Afmat.at<double>(1, 2) = trans.at<double>(0);
Afmat.at<double>(0, 2) = trans.at<double>(1);
warpAffine(image_moving, affine_result, Afmat, image_moving.size());

1 个解决方案

#1

The issue was that I was using points in row,column order whereas warpAffine wants a matrix derived from points in x,y order (aka column,row). Flipping the points and using getAffineTransform solved the issue.

问题是我在行,列顺序中使用点,而warpAffine想要一个从x,y顺序(也就是列,行)中的点派生的矩阵。翻转点并使用getAffineTransform解决了这个问题。