【作者】 刘春英；

【导师】 董金祥；

【作者基本信息】 浙江大学 ， 计算机应用技术， 2009， 博士

【摘要】 随着我国纺织印染行业的发展,人们迫切需要提高数字加网技术,以适应日益增长的市场需求和应对国际纺织印染市场的挑战。如何利用计算机图像处理技术去提高数字加网的效率以及品质,是数字加网系统的关键所在。本文针对其中的关键环节开展研究工作,取得的研究成果包括:在莫尔花纹的问题上,为了避免莫尔花纹现象,本文应用了基于抖动矩阵的方法生成网点中心。为了选择满足印花工艺网点中心分布要求的抖动矩阵访问路径,本文对不同的访问路径算法进行探讨和研究,并对不同的访问路径生成的网点中心分布进行傅立叶分析。在提高加网速度的问题上,本文提出了一种改进的逐点插入算法生成Delaunay三角网。传统的逐点插入算法具有内存占用小,支持动态生成三角网,易实现等优点,在传统的印花加网工艺中得到广泛应用。但由于其时间复杂度高,影响了整个加网过程的时间效率。传统的逐点插入法算法时间主要耗费在定位三角形上,本文提出一种基于方向搜索的定位三角形的新方法,根据三角网的点、线、面的拓扑关系来定位插入点所在的三角形,以避免全局搜索,提高了动态插入点的效率,从而提高三角网构网效率。在网点面积大小的均匀化问题上,本文提出了一种基于误差扩散的算法,有效地解决了网点大小不均匀的问题。为了从根本上避免莫尔花纹现象,根据传统印花工艺的要求,网点的中心分布一般应该满足随机性好的要求。虽然随机访问路径生成的网点中心分布相对于其它访问路径而言有更好的随机性,但由于过于提倡随机性和依赖随机访问路径,容易产生畸形网点,会导致最终网点区域大小的不可控。本文提出的均匀化算法就是为了解决如何在使用和发挥随机访问路径优势的同时,缓解和减轻随机性带来的负面效果,并且优化后的数字加网算法能够保持高效性和实时性的问题。本文利用的是误差扩散的思想,在处理需要调节的网点时,将该网点面积与平均值的差值扩散到周围网点,使畸形网点的面积趋于网点面积的平均值。综合上述算法,本文实现了一个数字加网的原型系统。该系统的设计参考了传统的数字加网的流程,其中各模块的核心就是本文所研究的各个算法。同时,系统提供了用户交互模块,支持用户对网点中心的生成、网点区域的确定等模块进行设置,选择不同的算法。本原型系统的开发旨在对数字加网流程中的各个模块的算法进行研究改进,是对数字加网技术的有益探索。更多还原

【Abstract】 With the development of Textile Printing of our country, the technique of digital halftoning is required to be improved urgently, in order to meet the needs of the growing market and the challenges of the world market. How to improve the efficiency of the halftoning process and the quality of the halftoning results is the key problem of designing the digital halftoning system by using digital image processing technology. Some efforts have been performed on several key issues in the dissertation. The main contributions of the thesis include:On the study of the moire problem, this thesis proposes an algorithm for building stochastic-dot screens based on the dither matrix to avoid the moire pattern. To choose the visiting path that meets the demand of digital halftoning, we study several kinds of visiting paths and analyze them by using Fourier-analysis.On the study of improving the efficiency of digital halftoning, this thesis proposes an improved incremental Delaunay triangulation algorithm. The traditional incremental algorithm has the advantages of utilizing less system memory, inserting points dynamically, easy to implement, and so on. However, the efficiency of the traditional incremental algorithm is low, which will affect the efficiency of the halftoning process. We present a simple enhancement for locating the point to be inserted by using the topological relationships between the triangles. The triangle containing the inserted point can now be found faster.On the study of the homogenization of the screen dots, this thesis proposes a homogenization algorithm based on the error diffusion algorithm. Traditionally, to avoid the moire pattern, the screen dots are required to be distributed randomly. Although the random visiting paths meet the demand perfectly, they will also bring some screen dots that with long and narrow shapes which will affect the quality of the halftoning images. The maximal screen surface of different dots will also vary considerably. The homogenization algorithm we proposed is to weaken the negative effects brought by the random visiting paths while maintaining the efficiency of the halftoning algorithm. Our method is based on the idea of the error diffusion algorithm, by diffusing the error between the surface of the dot and the average surface of all dots to the adjacent dots to reduce the surface difference between different dots.Based on the algorithms mentioned above, we develop a prototype system of digital halftoning. The system process is designed according to process of digital halftoning. The core of each module is the algorithm studied in our thesis. In addition, the interactive model is provided for selecting different algorithms for the Delaunay triangulation, the way to determine the maximal screen dot surface, and so on. This prototype system is for the purpose of studying and improving the key algorithms in digital halftoning. It is also a helpful exploration on digital halftoning.更多还原