As SIFT features are invariant to rotation and scaling, we employ SIFT to extract feature points.

由于SIFT特征对旋转和缩放具有不变性，该算法利用SIFT提取图像的特征点。

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And Scale Invariant Feature Transform (SIFT) was employed to exclude those sub-regions with smaller matching key points.

然后利用尺度不变特征变换(SIFT)剔除那些匹配的关键点数目少的子区域。

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