基于 2 个灭点和局部尺度的三维空间尺度估计

三维空间尺度估计是三维重建中的一个重要工作，现实世界中也存在一些基于单幅图像进行三维空间尺度估计的需求。通常情况下，尺度估计需先对相机进行标定。根据单目图像符合透视原理的特性，提出了一种基于 2 个灭点和局部尺度信息的方法对相机进行标定，从而得到单目图像物体中三维空间尺度信息的估计。首先，从单目图像中选择 2 组互相正交的平行线组，得到对应 2 个灭点的坐标；然后，利用灭点坐标和焦距信息得到世界坐标系和相机坐标系之间的旋转矩阵，再利用灭点的性质和已知局部尺度信息得到平移向量，完成单目相机的标定；最后，还原二维图像中像素点对应的三维世界坐标值，计算出图像中 2 个像素点在三维空间的尺度信息。实验结果表明，该方法能有效地对单幅图像中的建筑物体进行尺度估计。

3D spatial scale estimation based on two vanishing points and local scale

3D spatial scale estimation is of great significance to 3D reconstruction, and is in demand in the real world in the case of a single image. Generally, the camera must be calibrated before the scale estimation. According to the perspective principle of the monocular image, a method based on two vanishing points and local scale information was proposed to calibrate the camera, thereby obtaining the estimation of the 3D scale information in the monocular image. Firstly, two orthogonal groups of parallel lines were selected from the monocular image to produce the coordinates of two vanishing points. Then the rotation matrix between the world coordinate system and the camera coordinate system was yielded using the vanishing point coordinate and the focal length information. The translation vector was also acquired through the property of vanishing point and the known local scale information. Finally, the 3D worldcoordinates corresponding to the pixels in the 2D image were restored to calculate the 3D scale information. Experimental results show that this method can effectively estimate the scale of building objects in a single image.