一种加网图像去网的算法

A Computing Method of Descreen for Halftone Image

采用查找网点中心的方法,计算出任意加网图像的网点网格,按网格中网点的面积率来转换成灰度值,改变二值图属性,从而达到去网的目的。实验结果表明,去网效果与加网图像的分辨率、加网线数、加网角度等因素有关。使用此算法可以得到较满意的去网效果,可以合成出满足打样要求的彩色图像,用于RIP后图像的数字打样。

The descreen methods for color or grayscale images captured by scanner are generally blur arithmetic. But for halftone image generated by RIP the blur arithmetic is useless because the image is bi-level bitmap one so that it is of only 0 and 1 two levels. The descreen method is based on a very different arithmetic, it finds out the center of halftone cell and screen ruling parameters first, and then divides the image into halftone cell. By computing dot area percentage in each halftone cell and converting its value to the grayscale, the halftone dots would be eliminated. The computing results show that the descreening results dependent upon the resolution, screen ruling angle and frequency of the halftone image. The descreen effect of this method is reasonable good and a full color image can be composed from 4 RIPed separation images. The method can be used to digital soft proof based on the RIPed separation images.