基于自适应中值滤波的逆半调算法

针对误差分散半调图像，提出了一种基于自适应中值滤波的逆半调算法。该算法是在传统低通滤波逆半调算法基础上进行改进，先用一个大小为11×11、方差为1.3的高斯低通滤波器对半调图像A进行平滑处理，利用自适应中值滤波器得到图像B，在平滑非脉冲噪声的同时试图保留细节；然后通过带通滤波器得到图像B的边缘，并对边缘进行去噪增强处理，得到边缘图像F；最后把处理后的边缘图像F以一定的增益倍数与图像B进行线性相加，得到最终逆半调图像。试验结果表明，该算法在进行图像平滑的同时有效地保留了图像细节，处理后的图像的峰值信噪比比传统低通滤波方法高，图像的信息熵也有了提高。

Inverse Halftoning Algorithm Based on Adaptive Median Filter

In view of error diffusion halftone image, an inverse halftoning algorithm based on adaptive median filter is proposed, which improved from the traditional low-pass filtering inverse halftoning algorithm. Firstly, the algorithm smoothes the halftone image A with a Gaussian low-pass filter whose size is 11×11 and variance is 1.3, obtains the image B by adaptive median filter and smoothes non-impulse noise while trying to preserve the details. Secondly, gets the edge of image B by band-pass filter and the edge image F by de-nosing and enhancing the edge of image B. Finally, obtains the final inverse halftoning image by integrating F and B in a certain gain multiple. The experimental results show that the algorithm can not only make the image smoothly but also retain the details of the image, and the PSNR and IN of the processed image is better than the traditional low-pass filtering.