顾及边缘信息的多尺度误差扩散半色调算法

目的为了解决传统多尺度误差扩散半色调算法会导致半色调结果图像阶调变暗和边缘模糊的问题,提出一种顾及边缘信息的多尺度误差扩散半色调算法。方法根据当前像素邻域内像素点的处理状态,设计动态非时序误差扩散滤波器;利用图像局部平均灰度与空间变化率提取图像边缘信息,结合图像边缘信息与灰度信息确定半色调处理顺序。结果半色调处理结果视觉效果均匀,阶调信息和边缘结构信息与原图像一致性良好,峰值信噪比、加权信噪比和结构相似度分别提高了0.7～1.2 d B,0.9～1.5 d B,0.11～0.18。结论该算法解决了多尺度误差扩散算法的图像阶调变暗和边缘模糊的问题,有效提高了半色调输出质量。

Multi-scale Error Diffusion Halftone Algorithm Considering Edge Information

The work aims to put forward a multi-scale error diffusion halftone algorithm considering edge information, in order to solve the problems of tone darkening and edge blurring of the resulting halftone image caused by the traditional multi-scale error diffusion halftone algorithm. Firstly, a dynamic non-causal error diffusion filter was designed according to the states of the pixel points in the neighborhood of the pixel being processed currently. Then, the image edge information was extracted by means of the local average gray scale and spatial change rate of the image. Finally, the halftone processing sequence was determined by combining the edge and gray scale information. The visual effect of halftone processing results was uniform. The tone and edge structure information was well consistent with the original image. PSNR, WSNR and SSIM were respectively improved by 0.7-1.2 dB, 0.9-1.5 dB and 0.11-0.18. The proposed algorithm solves the problems of tone darkening and edge blurring of the multi-scale error diffusion algorithm, thus effectively improving the halftone output quality.