摘要(英) |
In this thesis, we focus on solving the problem of uneven light effect on document images. A method based on EMD theorem is proposed to estimate and rectify the light-field. Our proposed method does not need to extract the IMF signal and only need to consider the max-envelope instead of all envelopes and residue function in EMD to obtain the light-field distributions of images. Our system consists of three parts including max-envelope calculation, light-field distribution adjustment, and signal scale adjustment.
In the first part, we first use fast method, least-squares approximation, to find max-envelope form input signal scale via one dimensional way. In the second part, we observe the distributions of max-envelope and signal to find the max differential point between light-fields as the cut points. Then, segment the signal by the cut points and calculate local max-envelopes to obtain closer light-field distribution of original signal. In the third part, we will set the contrast value depending on light-field intensity and enhance the gray scale signal. The contrast value will be fixed if it is an over-exposure signal. Last, enhance gray scale signal by contrast value and finally adjust the enhanced gray scale.
Experimental results show that our method exhibits good outcome about removing over-exposure, shadow, reflection and back-light effects on document images. Besides, the execution time is much faster than EMD and the recognition result can achieve the same efficiency of EMD method.
As to the color image uneven light-field effect, we calculate the max-envelope by “Triangle Linear Interpolation”, and adjust the value-element (V of HSV color system) to conserve the property of continuous color information. Experimental results demonstrate that our proposed method performs well on color images too.
|
參考文獻 |
[1] Norden E. Huang ,"The Empirical Mode Decomposition and The Hilbert Spectrum for Nonlinear and Non-stationary Time Series Analysis , "NASA.(manuscript) , 1996.
[2] Norden E. Heng Shen , Steven R. Long , Manli C. Wu , Hsing H. Shih , Quanan Zheng , Nai-Chyuan. Yen , Chi Chao Tung , and Henry H. Liu , "The Empirical Mode Decomposition and The Hilbert Spectrum for Nonlinear and Non-stationary Time Series Analysis ," Proc. R. Sec. London A , The Royal Society , pp. 903-995, 1998.
[3] Soo-Chang Pei and Feng-Ju Chang,"Effective color constancy method under uniform of non-uniform illuminant",23th Conf. in Computer Vision, Graphics and Image Processing(CVGIP), 2010
[4] Soo-Chang Pei and Mary Tzeng "Uneven Illumination Removal and Image Enhancement Using Empirical Mode Decomposition," 20th Conf. in Computer Vision, Graphics and Image Processing(CVGIP), 2007.
[5] Hany Farid and Edward H. Adelson,"Separating Reflections and Lighting Using Independent Components Analysis," in IEEE Computer Society Conf. Computer Vision and Pattern Recognition, vol. 1, June 23-25 , pp. 262-267. 1999
[6] Yen-Wei Chen,Gang Xu and Masaki Yamazaki , " Separation of Reflection Components by Kernel Independent Component Analysis" in 18th Int. Conf. Pattern Recognition(ICPR), vol. 3, pp. 194-197 , 2006
[7] Sei-Wang Chen,Yun-Chung Chung ,Shyang-Lih Chang and Jung-Ming Wang, "Interference Reflection Separation from a Single Image" Applications of Computer Vision (WACV),pp.001-006 ,2009
[8] Chien-Hsing Choua, Wen-Hsiung Linb and Fu Changb , " A binarization method with learning-built rules for document images produced by cameras ",Pattern Recognition ,Volume 43, Issue 4, Pages 1518-1530 , April 2010
[9] Shijian Lu, Chew Lim Tan and Bolan Su "Document image binarization using background estimation and stroke edges", International Journal on Document Analysis and Recognition , Volume 13 Issue 4, December 2010
[10] Jean Claude Nunes, Yasmina Bouaoune, Eric Delechelle, Oumar Niang, Philippe Bunel, "Image Analysis by Bidimensional Empirical Mode Decomposition", Image and Vision Computing, vol. 21, pp.1019- 1026, 2003.
[11] Shuen-De Wu , Liang-Jung Chen , Chiu-Wen Wu,Guan-Yu Chen and Chia-Chi Lin , "Improving the computational efficiency of empirical mode decomposition algorithm by down sampling ", International Journal of Advanced Information Technologies (IJAIT) , Vol. 4 , No. 2 , 2010。
[12] 吳順德,陳思予,陳虹伯“經驗模態分解法之研究趨勢探討與問題分析” ,臺北科技大學學報, No.42-1, 2009。
[13] 吳政憲,「希爾伯特阻尼頻譜於高樓損傷評估之應用」,國立中央大學土木工程研究所,碩士論文,民國 90 年
[14] Ron Larson and Bruce H. Edwards, Elementary Linear Algebra 4th ed., Houghton Mifflin Company, 2000.
[15] Marc Ebner, "Color constancy base on local space average color" ,Machine Vision and Applications, vol. 11, No. 5, July, 2009.
[16] Joost van de Weijer, Theo Gevers, and Arjan Gijsenij, "Edge-Based Color Constancy" ,IEEE Trans. on image processing, Vol. 16, No. 9, September 2007.
|