图像误差扩散半色调技术研究

发布时间：2018-05-16 09:24

本文选题：数字半色调 + 误差扩散　；参考：《湖南工业大学》2017年硕士论文

【摘要】：数字半色调技术是联系模拟原稿或物理场景数字化转换与印刷的桥梁,是数字印刷乃至现代化印刷的关键、核心技术之一。目前这项技术已经被广泛应用到了印刷、水印、信息加密技术、图像压缩、图像传输,医学图像分析处理等各个与人们生活水平息息相关领域中。所有这些技术领域无一不与人们的生活息息相关,这决定了数字半色调技术在现代图像处理领域中扮演了极其重要的角色,在硬拷贝输出和显示领域具有非常重要的实用意义。显然,误差扩散半色调算法作为数字半色调技术的重要分支具有十分重要的研究价值,本文主要工作如下:1)当前误差扩散算法采用的扫描方式主要有光栅扫描、蛇形扫描、空间填充曲线扫描。光栅、蛇形扫描误差扩散半色调算法在输出半色调图像的高光和暗调区域存在明显的蠕虫现象,在中频区域存在明显的结构性纹理;基于空间填充曲线的误差扩散半色调算法虽然有效降低了半色调图像中的蠕虫现象,但同时引入了噪声。鉴于以上原因,提出了一种基于间断扫描方式的误差扩散半色调算法,同时将固定的量化阈值改为自适应的量化阈值。在间断扫描方法中,会根据当前像素点所处的灰度等级有选择性的挑选误差扩散滤波器。与蛇形扫描和光栅扫描方式相比,间断扫描方式在处理同行像素点的时候,量化误差能够左右双向传播,有效的缓解了蠕虫现象的形成,提高了半色调图像的质量。2)提出了一种基于改进误差扩散滤波器的半色调算法和基于平均灰度与对比度联合的半色调图像质量评价方法。改进的误差扩散滤波器与传统的误差扩散滤波器相比能够使得量化误差扩散范围更广,能更有效的阻止蠕虫链的形成且没有引进额外的噪声,在提高半色调图像质量的同时也没有增加额外的计算复杂度。
[Abstract]:Digital halftone technology is a bridge between digital conversion and printing of analog manuscripts or physical scenes. It is the key and one of the core technologies of digital printing and even modern printing. At present, this technology has been widely used in printing, watermarking, information encryption technology, image compression, image transmission, medical image analysis and processing and other fields closely related to people's living standards. All these technical fields are closely related to people's lives, which determines that digital halftone technology plays an extremely important role in the field of modern image processing and has very important practical significance in the field of hard copy output and display. Obviously, the error diffusion halftone algorithm as an important branch of digital halftone technology has very important research value. The main work of this paper is as follows: (1) the scanning methods used in the current error diffusion algorithm are mainly raster scanning, snake scanning. Space filling curve scan. Raster, serpentine scan error diffusion halftone algorithm has obvious worm phenomenon in the output halftone image's high light and dark tone region, and obvious structural texture in the intermediate frequency region. Although the error diffusion halftone algorithm based on the space filling curve can effectively reduce the worm phenomenon in the halftone image, noise is introduced at the same time. In view of the above reasons, an error diffusion halftone algorithm based on discontinuous scanning is proposed, and the fixed quantization threshold is changed to an adaptive quantization threshold. In the discontinuous scanning method, the filter is selected selectively according to the gray level of the current pixel. Compared with the snake-like scanning and raster scanning, the quantization error can propagate in both directions when processing the peer pixels, which effectively alleviates the formation of worm phenomenon. (2) A halftone algorithm based on improved error diffusion filter and a method for evaluating the quality of halftone images based on the combination of average gray and contrast are proposed. Compared with the traditional error diffusion filter, the improved error diffusion filter can make the quantization error spread wider, prevent worm chain from forming more effectively and do not introduce extra noise. While improving the halftone image quality, there is no additional computational complexity.
【学位授予单位】：湖南工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP391.41

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