分阶调调频网点结构形态提取方法及评价

Study and Appraise on the Extraction Method of Whole Tone FM Dot Microscopic Structure

调频网点是数字印刷中常用的网点类型,其微观形态决定印刷品质量。研究在分析网点图像特性的基础上,提出一种分阶调准确提取调频网点结构形态的方法。利用光学显微系统采集喷墨印刷样张上的网点图像,随着网点面积率的增加,图像中目标与背景灰度差异逐渐减小,无法通过单一的图像处理方法获得全阶调范围内的准确网点边缘。根据网点灰度直方图从双峰图过渡到单峰图的特性,对双峰网点图像提出了一种结合中值滤波器、非极大值抑、最大类间方差法和细化的边缘提取方法;而针对单峰图像提出一种根据灰度级函数切线斜率变化特征,寻找最佳阈值二值化的算法。研究中提出的分阶调算法能有效抑制背景噪声,较大程度保留网点边缘信息;且与实际测量值有较高的吻合度,达到了准确提取网点结构的目的。研究成果对于客观评价喷墨印刷质量有一定的理论价值。

FM dot type is commonly used in digital printing. Dot＇ s morphological characteristics effect the printing quality directly. An extraction method of whole tone FM dot microscopic structure which by the FM image＇ s features is presented. By using the optical microscopy, the dot image on the ink jet printing proof is collected. With the increase of dot area, the gray differences between the target image and the background decrease. It means that cant get all tone dots＇ edge by only one method. The different methods are presented according to the unimodal and bimodal gray histogram. By using the median filter,maximum inhibition, binarization and refinement, the ima- ges＇ dot edge are extracted. Based on the grayscale function tangent slope characteristics to search for the best threshold binarization algorithms, which put forward a kind of extract unimodal images＇ dot edge. The algorithm proposed can effectively restrain background noise, largely retain edges. The results tally with the actual values, achieved the accurate dot structure. This research has certain theoretical value in objectively evaluating the ink-jet printing＇ s quality.