3种阈值方法在闪电通道图像识别中的应用
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摘要
该文实现了3种常见的阈值算法在闪电通道识别中的应用。针对某些闪电通道图像对比度较低的特点,首先对原始图像去除背景光照不均的影响并进行图像增强,再根据所处理的闪电通道图像的具体情况,选择全局自适应阈值法、局部自适应阈值法或基于Otsu自适应阈值的Canny算子对增强后的图像进行边缘检测,进而对闪电通道进行识别。对所提取到的闪电通道进行形态学和细化处理,最终提取到由连续的像素点序列表示的闪电通道。针对数字图像中闪电通道背景的不同特点,文中提到的3种阈值方法能够有针对性地对不同图像进行通道检测,在保证准确获得清晰边缘信息的同时,较好地兼顾了对弱边缘信息的提取,有效保证了对闪电通道的识别效果。
General digital cameras,camcorders as well as the BOYS camera specially developed for the lightning observation,are all important tools for lightning research.They are used to obtain the basic data for understanding geometry features of channels and main development processes of lightning.For a long time,extracting lightning channel coordinates from digital images is based on manual processing methods with the relatively low efficiency.With the development of the photoelectric techniques,more and more advanced optical devices are used in lightning observation,such as high-speed cameras and the Automatic Lightning Processing Feature Observation System(ALPS),and data obtained become much richer.How to automatically process these data and improve the efficiency of data extraction and analysis is an urgent need to be addressed.Considering the complexity of lightning discharges and various characteristics of the lightning channel,only one algorithm is not enough to obtain a satisfying recognition result in all situations.Therefore,3common threshold methods are applied jointly in the lightning channel recognition.Firstly,the impact of the uneven illumination is eliminated by subtracting the background and the contrast of the image is enhanced.Secondly,global adaptive threshold method,local adaptive threshold method or adaptive Canny operator method is applied for edge detection.And then,morphological and thinning processes are carried out to get the lightning channel represented by the continuous sequence of pixels.Considering different characteristics of the lightning channel digital image,selecting appropriate algorithm can ensure getting a clear edge information even including weak edges,guaranteeing a good recognition effect finally.Through experiments,it can be concluded that for the lightning channel with simple structure and relatively uniform brightness,all algorithms mentioned above can get a good recognition result,among which the global adaptive threshold method is simpler and more efficient.Local adaptive threshold method can calculate the threshold for different images universally.And for the low-contrast images with a smooth background,using adaptive Canny operator method can achieve a satisfactory recognition result.
General digital cameras,camcorders as well as the BOYS camera specially developed for the lightning observation,are all important tools for lightning research.They are used to obtain the basic data for understanding geometry features of channels and main development processes of lightning.For a long time,extracting lightning channel coordinates from digital images is based on manual processing methods with the relatively low efficiency.With the development of the photoelectric techniques,more and more advanced optical devices are used in lightning observation,such as high-speed cameras and the Automatic Lightning Processing Feature Observation System(ALPS),and data obtained become much richer.How to automatically process these data and improve the efficiency of data extraction and analysis is an urgent need to be addressed.Considering the complexity of lightning discharges and various characteristics of the lightning channel,only one algorithm is not enough to obtain a satisfying recognition result in all situations.Therefore,3common threshold methods are applied jointly in the lightning channel recognition.Firstly,the impact of the uneven illumination is eliminated by subtracting the background and the contrast of the image is enhanced.Secondly,global adaptive threshold method,local adaptive threshold method or adaptive Canny operator method is applied for edge detection.And then,morphological and thinning processes are carried out to get the lightning channel represented by the continuous sequence of pixels.Considering different characteristics of the lightning channel digital image,selecting appropriate algorithm can ensure getting a clear edge information even including weak edges,guaranteeing a good recognition effect finally.Through experiments,it can be concluded that for the lightning channel with simple structure and relatively uniform brightness,all algorithms mentioned above can get a good recognition result,among which the global adaptive threshold method is simpler and more efficient.Local adaptive threshold method can calculate the threshold for different images universally.And for the low-contrast images with a smooth background,using adaptive Canny operator method can achieve a satisfactory recognition result.
引文
[1]王道洪,郄秀书,郭昌明.雷电与人工引雷.上海:上海交通大学出版社,2000:1-12.
[2]张义军,周秀骥.雷电研究的回顾和进展.应用气象学报,2006,17(6),829-834.
[3]刘欣生,肖庆复.人工引发雷电的静态摄影及特性分析.高原气象,1998,17(l):106-110.
[4]张义军,孟青,马明,等.闪电探测技术发展和资料应用.应用气象学报,2006,17(5):611-620.
[5]李俊,张义军,吕伟涛,等.一次多回击自然闪电的高速摄像观测.应用气象学报,2008,19(4):401-411.
[6]张义军,吕伟涛,郑栋,等.负地闪先导-回击过程的光学观测和分析.高电压技术,2008,34(10):2022-2028.
[7]王才伟,刘欣生,董万胜,等.人工触发闪电通道的发光特征.高原气象,1998,17(1):10-23.
[8]吕伟涛,张义军,周秀骥,等.火箭触发闪电通道的亮度特征分析.气象学报,2007,65(6):983-993.
[9]孔祥贞,郄秀书,王才伟,等.首次回击具有双接地点的地闪光学和电学特征的个例分析.高原气象,2003,22(3):259-266.
[10]Zhou Enwei,Lu Weitao,Zhang Yang,et al.Correlation analysis between the channel current and luminosity of initial continuous and continuing current processes in an artificially triggered lightning flash.AtmosRes,2013,129:79-89.
[11]Lu Weitao,Zhang Yijun,Li Jun,et al.Optical observations on propagation characteristics of leaders in cloud-to-ground lightning flashes.Acta Meteor Sinica,2008,22(1):66-76.
[12]周恩伟.触发闪电放电过程的光电同步观测与分析.北京:中国科学技术大学,2010.
[13]Otsu N.A threshold selection method from gray level histograms.IEEE Trans Systems,Man and Cybernetics,1979,9(1):62-66.
[14]杨俊,吕伟涛,马颖,等.基于局部阈值插值的地基云自动检测方法.气象学报,2010,68(6):1007-1017.
[15]梁光明,孙即祥,马琦,等.Otsu算法在Canny算子中的应用.国防科技大学学报,2003,25(5):36-39.
[16]武斌,张广庶,王彦辉,等.双接地负地闪VHF辐射源放电通道和光学通道的对比分析.高原气象,2013,32(2):519-527.
[17]杨俊,吕伟涛,马颖,等.基于自适应阈值的地基云自动检测方法.应用气象学报,2009,20(6):713-720.
[18]Canny J.A computational approach to edge detection.IEEE Trans Pattern Analysis and Machine Intelligence,1986,8(6):679-698.
[19]Rafael C G,Richard E W.数字图像处理.阮秋琪,译.上海:电子工业出版社,2007:423-431.
[20]杨威,郭科,魏义坤.一种有效的基于八邻域查表的指纹图像细化算法.四川理工学院学报,2008.21(2):61-62.
[21]高太长,刘磊,赵世军,等.全天空测云技术现状及进展.应用气象学报,2010.21(1):101-106.
[22]朱彪,杨俊,吕伟涛,等.基于KNN的地基可见光云图分类方法.应用气象学报,2012,23(6):722-727.
[2]张义军,周秀骥.雷电研究的回顾和进展.应用气象学报,2006,17(6),829-834.
[3]刘欣生,肖庆复.人工引发雷电的静态摄影及特性分析.高原气象,1998,17(l):106-110.
[4]张义军,孟青,马明,等.闪电探测技术发展和资料应用.应用气象学报,2006,17(5):611-620.
[5]李俊,张义军,吕伟涛,等.一次多回击自然闪电的高速摄像观测.应用气象学报,2008,19(4):401-411.
[6]张义军,吕伟涛,郑栋,等.负地闪先导-回击过程的光学观测和分析.高电压技术,2008,34(10):2022-2028.
[7]王才伟,刘欣生,董万胜,等.人工触发闪电通道的发光特征.高原气象,1998,17(1):10-23.
[8]吕伟涛,张义军,周秀骥,等.火箭触发闪电通道的亮度特征分析.气象学报,2007,65(6):983-993.
[9]孔祥贞,郄秀书,王才伟,等.首次回击具有双接地点的地闪光学和电学特征的个例分析.高原气象,2003,22(3):259-266.
[10]Zhou Enwei,Lu Weitao,Zhang Yang,et al.Correlation analysis between the channel current and luminosity of initial continuous and continuing current processes in an artificially triggered lightning flash.AtmosRes,2013,129:79-89.
[11]Lu Weitao,Zhang Yijun,Li Jun,et al.Optical observations on propagation characteristics of leaders in cloud-to-ground lightning flashes.Acta Meteor Sinica,2008,22(1):66-76.
[12]周恩伟.触发闪电放电过程的光电同步观测与分析.北京:中国科学技术大学,2010.
[13]Otsu N.A threshold selection method from gray level histograms.IEEE Trans Systems,Man and Cybernetics,1979,9(1):62-66.
[14]杨俊,吕伟涛,马颖,等.基于局部阈值插值的地基云自动检测方法.气象学报,2010,68(6):1007-1017.
[15]梁光明,孙即祥,马琦,等.Otsu算法在Canny算子中的应用.国防科技大学学报,2003,25(5):36-39.
[16]武斌,张广庶,王彦辉,等.双接地负地闪VHF辐射源放电通道和光学通道的对比分析.高原气象,2013,32(2):519-527.
[17]杨俊,吕伟涛,马颖,等.基于自适应阈值的地基云自动检测方法.应用气象学报,2009,20(6):713-720.
[18]Canny J.A computational approach to edge detection.IEEE Trans Pattern Analysis and Machine Intelligence,1986,8(6):679-698.
[19]Rafael C G,Richard E W.数字图像处理.阮秋琪,译.上海:电子工业出版社,2007:423-431.
[20]杨威,郭科,魏义坤.一种有效的基于八邻域查表的指纹图像细化算法.四川理工学院学报,2008.21(2):61-62.
[21]高太长,刘磊,赵世军,等.全天空测云技术现状及进展.应用气象学报,2010.21(1):101-106.
[22]朱彪,杨俊,吕伟涛,等.基于KNN的地基可见光云图分类方法.应用气象学报,2012,23(6):722-727.