National Key Technology Research and Development Program of the Ministry of Science and Technology (No.2014BAB12B03);National Natural Science Foundation of China (No.61501077);Fundamental Research Funds for the Central Universities (No.3132016351)
The technique of histogram equalization (HE) is widely used in the field of image enhancement
the method is introduced into the gradient field in this paper
so image details are distributed in each gray level uniformly.Moreover
the characteristics of the histogram of gradient magnitude are studied
according to the right-skewed distribution of gradient magnitude
the gradient field is equalized by two intervals.In terms of the threshold's selection
numerical characteristics of frequency distribution are considered
two standards of the interval threshold are proposed
which can divide the gradient magnitude into the interval with low magnitude and the interval with high magnitude.On the process of the reconstruction of target gradient field
matrix transform method is proposed
which substitutes the traditional method difference and iteration method
the proposed method can decrease the algorithm's time complexity.The experimental results show that the method this paper proposed can make image details enhance effectively.