基于灰度变换的水下焊接图像对比度增强  

Contrast Enhancement of Underwater Welding Image Based on Gray Scale Transformation

作　　者：张志伟 叶建雄[1] 程群 刘承林 钱江昆 ZHANG Zhiwei;YE Jianxiong;CHENG Qun;LIU Chenglin;QIAN Jiangkun(Jiangxi Province Key Laboratory of Precision Drive&Control,Nanchang Institute of Technology,Nanchang 330099,China;Leping No.1 Middle School of Jiangxi Province,Leping 333300,China)

机构地区：[1]南昌工程学院江西省精密驱动与控制重点实验室,江西南昌330099 [2]江西省乐平市第一中学,江西乐平333300

出　　处：《热加工工艺》2021年第7期127-131,共5页Hot Working Technology

基　　金：江西省研究生创新专项资金项目(YC2019-S430);江西省教育厅科技项目(GJJ180937)。

摘　　要：对比度增强是图像增强的关键技术。水下焊缝图像具有对比度低、灰度分布范围窄等缺陷,造成焊缝边缘难以提取,有必要应用此技术对原始图像进行预处理。灰度变换技术可以使灰度值映射至灰度全域,进而增强图像的焊缝信息。首先提出一种基于幂律灰度变换的改进型分段幂律曲线,使曲线呈S形分布,以对灰度的中段实现最大程度的拉伸,而对始末段的灰度拉伸较小;然后运用Otsu算法提取焊缝边缘区域的阈值,以该阈值作为分段曲线的分段点,从而把焊缝的边缘信息集中在曲线中段,可以有效提高焊缝边缘信息的对比度。试验证明,本文所述技术较直方图均衡化和经典幂律变换所获得的增强后图像质量明显更好,尤其是焊缝的边缘区域。Contrast enhancement is the key technology of image enhancement. The underwater weld image has the defects of low contrast and narrow gray distribution, which makes it difficult to extract the edge of the weld. It is necessary to apply this technology to preprocess the original image. Gray transformation technology can map the gray value to the whole gray area, and then enhance the seam information of the image. Firstly, an improved piecewise power-law curve based on power-law gray level was proposed to make the curve distribute in S shape, so as to stretch the middle part of gray level to the maximum extent, but to stretch the gray-level of the initial and end parts in smaller extent. Then, Otsu algorithm was used to extract the threshold of the edge area of the weld seam, and the threshold was used as the piecewise point of the piecewise curve. The edge information of the weld was concentrated in the middle of the curve, which could effectively improve the contrast of the edge information of the weld. The experiments show that compared with histogram equalization and classical power law transformation, the technology in this paper can obtain much better enhanced image quality, especially in the edge area of the weld.

关 键 词：水下焊接 图像增强 OTSU算法 幂律灰度变换 

分 类 号：TG409[金属学及工艺—焊接]