等面积递归分解的部分重叠局部直方图均衡

针对现有的直方图均衡算法在图像细节信息增强的同时无法保持输入图像亮度的缺点，以部分重叠局部直方图均衡算法（POSHE）为基础，将递归分解的思想引入子块图像直方图均衡过程，提出了一种改进的部分重叠局部直方图均衡算法。子块图像根据其累积概率密度（CDF）的中值递归地进行不同深度的分解，然后对每一个分解的子图像在其灰度范围内进行直方图均衡，并将均衡后的子图像合并，最后根据移动步长对子块图像进行线性或双线性插值消除块效应对图像细节信息的影响。实验结果表明，这种算法既能有效地增强图像的细节信息，又能保持输入图像的亮度，并且彻底地消除了块效应对图像均衡结果的影响，使均衡后的图像具有更加自然的视觉效果。

Partially overlapped sub-block histogram equalization based on recursive equal area separateness

The traditional histogram equalization is unable to keep the input image brightness, when enhancing the image details. Based on partially overlapped sub-block histogram equalization algorithm (POSHE), recursive separateness method is used in the process of sub-block histogram equalization. An advanced partially overlapped local histogram equalization algorithm is proposed. The sub-block image is separated recursively into different sub-images with the cumulative density function (CDF). Then each sub-image histogram is equalized within its respective gray range, and all the sub-images are incorporated into the equalized sub-block. Both linear and bilinear interpolation are used in the equalized sub-block based on step size avoiding the generation of the blocking effects and the influence on the image details. The simulation results show that the local details are enhanced, and the input image brightness is also preserved effectively. Finally, the influence on the image details is eliminated by avoiding the blocking effects, and more natural visual impression can be seen in the equalized image.