由未标定手持相机拍摄的图片构造全景图

Building Panoramas from Photographs Taken with An Uncalibrated Hand-Held Camera

提出了一种利用普通未经标定的相机,在近似固定位置拍摄的图片,来构造水平方向360°全景图的方法.一般来说这种图片可能存在透视变形较大、相邻图片重叠部分较小、亮度差异明显以及相机的倾斜和旋转等问题.这就使此类图像的配准和全景图拼接问题比采用经标定的相机或专用设备所拍摄的图片较为困难.因不宜直接采用简单的图像配准技术,文中特设计一种含梯度方向极稳健高效的特征匹配方法来对此类图像进行配准;同时提出了可靠的初始参数估计方法,并将求取相邻图像间透视变换参数的非线性优化过程简化为线性步骤,提高了运算速度和稳定性.实验结果表明,即使重叠区域很小(16%),该方法仍可获得较为满意的拼接效果.

This paper presents a method for building a full view cylindrical panorama from uncalibrated photos taken naturally with an ordinary hand-held camera held at an approximately fixed location. Such photos usually have large perspective distortion, small overlap, brightness differences, and camera rotations such as tilt and roll. These characteristics make both image alignment and panorama building more difficult than using photos taken by cameras calibrated by special equipment. To align such images, simple registration techniques cannot be applied directly. This paper shows how these images can be registered by a particular robust feature matching scheme, which contains robust information of gradient direction; this paper also proposes a reliable initial parameter estimation method as well as an iterative approach with linear steps to perspective transformation parameter optimization for pairs of adjacent images. Experiments show that the method yields good results even when the overlap region of adjacent photos is as small as 16%.