"华南虎"照片的摄像测量研究

2007年10月,华南虎照片一经公布,即引起各方关注。"挺虎派"和"打虎派"都极力从各个角度证明照片中华南虎的真伪,但采用的大都是定性分析方法。本文采用摄像测量方法,对照片中的华南虎进行了三维测量和重建,并进行了华南虎照与年画虎的相似度分析、虎照的细节变化分析等方面的研究。由于虎照之间的拍摄位置和角度变化不大,老虎部分的分辨率较低并存在模糊,用常规摄像测量方法难以重建三维结果。本文针对虎照实际情况,采用整体解算相机系统参数、局部重建老虎的方法,得到了满足精度要求的结果。结果表明,重建老虎不同部位的测量点均基本位于一个与像面基本平行的平面上。模拟场景实验证实了该重建方法正确可信。同时,根据平面物体的成像模型对虎照与年画虎进行了仿射校正和对比分析,表明照片虎与年画虎主纹理的骨架、轮廓基本重合,相似率为0.9986,满足平面变换条件。对眼部存在的差异也进行了分析。

Videometric Research on the Digital Photos of South China Tiger

The photos of a South China tiger have attracted a wide interest among scientists and scholars since they were released in October 2007. Both pros and cons of the tiger photos have so far made only qualitative analyses on whether the photos of the South China tiger are based on a real or fake tiger. This paper carries out three-dimensional measurements and reconstructions of the South China tiger from the photos using the videometrics, and also quantitative analyses on the similarity and difference of details of the tiger in the photos and that in the poster. Then the results of quantitative analysis are presented. It is unfeasible to reconstruct the tiger with high precision by conventional methods, considering the small viewpoint changes of photos, the low resolution of the tiger in the photos and the blur of image. To achieve a precise enough reconstruction of the tiger for its 3D recognition, an approach is employed, which computes multi-view geometry parameters from the feature points in the whole tiger photos, but reconstruct the tiger using local features. The results show that all the points on the face, trunk and legs of the tiger reconstructed from photos are nearly on a same plane which is parallel to the image plane. The experiments of simulating scenes have confirmed the reliability of the reconstruction. At the same time, the affine rectification and contrast analysis are made on the tiger images in the photos and the poster tiger, and the similarity coefficient is 0.998 6. It is shown that the main texture framework and contour of the tiger in the photos agree well with those of the poster tiger. In addition, the difference of eyes of the tigers in the photo and the poster is analyzed.