Question

我正在尝试在图像旋转后获取新的坐标。但是，我有一个相对坐标。所有四个坐标均由介于0和1之间的值组成。例如（x1，y1）= [0.15，0.15]（x2，y2）= [0.8，0.15]（x3，y3）= [0.8，0.8]（x4， y4）= [0.15，0.8] 当我将图像旋转n度时，我想获得新的x，y坐标。

image = Image.open(os.path.join('./AlignImages', image_name))

labels = np.array(list(map(float, a.split(" ")[1:]))).astype('float32')
#if labels == [0.1 0.1 0.5 0.1 0.5 0.5 0.1 0.5] [x1 y1 x2 y2 x3 y3 x4 y4]  
labels = np.vstack((labels[0::2], labels[1::2]))
# [0.1 0.5 0.5 0.1]    [x1 x2 x3 x4]
# [0.1 0.1 0.5 0.5]    [y1 y2 y3 y4]
print(labels)

labels = np.array([[labels[0][0]-0.5, labels[0][1]-0.5, labels[0][2]-0.5, labels[0][3]-0.5],[0.5-labels[1][0], 0.5-labels[1][1], 0.5-labels[1][2], 0.5-labels[1][3]]])
#This is to move the center point of the image.
#Adjust the value to rotate because the upper left corner of the image is (0, 0)
image = image.rotate(rotation_scale, expand=True)
#I gave the option to expand the image so that the rotated image was not cropped.

image.show()
rotation_ = np.array([[np.cos(rotation_scale), (np.sin(rotation_scale))],[-1*np.sin(rotation_scale), np.cos(rotation_scale)]])
#I have defined a transformation matrix.

src = np.matmul(rotation_, labels)
#Multiply the transformation matrix by the coordinates to obtain the new coordinates.


src = np.array([[src[0][0]+0.5, src[0][1]+0.5, src[0][2]+0.5, src[0][3]+0.5],[0.5+src[1][0], 0.5+src[1][1], 0.5+src[1][2], 0.5+src[1][3]]])
#Let the top left corner be 0, 0 again.

print(src)

[[ 0.24779222  1.00296445  0.7265248  -0.05902794]
 [ 0.8065444   0.41615766  0.2350563   0.60667523]]

但是，此代码似乎无效。我以为我可以在该源代码中获得旋转图像的四个相对坐标，但根本没有。我想获取扩展图像（旋转图像）中四个顶点的相对坐标。值都应在0到1之间。如何获得所需的四个坐标？

Answer 1

问题可能出在旋转点周围的中心点上。根据我在上一个项目中的经验，您需要知道中心点和度数

例如：您的图像围绕中心点（图像的中间点）向右旋转了90度，现在您需要将这些点围绕中心点向后旋转-90度。 c ++中的代码（对不起，我仅熟悉c ++，但是我认为您可以轻松地移植到python）

// the center point 
Point2f center=(width/2,height/2)

//the angle to rotate, in radiant 
// in your case it is -90 degree
double theta_deg= angleInDegree * 180 /M_PI;

// get the matrix to rotate
Mat rotateMatrix = getRotationMatrix2D(center, theta_deg, 1.0);

// the vector to get landmark points
std::vector<cv::Point> inputLandmark;
std::vector<cv::Point> outputLandmark;

// we use the same rotate matrix and use transform
cv::transform(inputLandmark, outputLandmark, rotateMatrix);

图像旋转后如何获取新坐标？

1 个答案: