This paper proposes a method to measure the inclination of a natural image on the basis of the distribution of edge directions of pixel pairs that represent the figures of the symmetrical objects in an image. This paper also describes a relation between the measured inclined angles by the proposal method and the visual inclined angles. The distribution of edge directions of pixel pairs is supposed to represent a global inclination of an image and the directions of symmetrical objects in the image. The proposed method measures the inclined angle of an image by evaluating the distribution of edge directions of pixel pairs and by extracting the peak in the distribution. The experimental results show that the measured inclined angles by the proposed method were similar to the visual inclined angles evaluated by the subjects.

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