期刊名称：ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
印刷版ISSN：2194-9042
电子版ISSN：2194-9050
出版年度：2008
卷号：XXXVII Part B6b
页码：171-176
出版社：Copernicus Publications
摘要：Aiming at uneven illumination and low contrast of large plane array CCD images, this paper presents an effective algorithm to extract uneven illumination from images and enhance the contrast by using wavelet transform. Based on an analysis of the illumination model on a focal plane, emulational images are constructed for the illumination model. Through analysis of the wavelet transform coefficients of emulational images, it is found that information of illumination non-uniformity mainly appears in wavelet approximate coefficients, and detail information is contained in detail coefficients. Taking advantage of this property, the original image is first decomposed with multiresolution wavelet, next, the natural logarithms of approximate coefficients are calculated, and an appropriate attenuating operator is applied to implement the non-uniformity correction of approximate coefficients before exponentiating correction, linear contrast-stretch is applied to all the approximate coefficients, a nonlinear function is applied to each level detail coefficients to accomplish adaptive contrast enhancement, finally, uniform illuminative and contrast enhanced aerial images are acquired through reconstruction of images. The experiments show that the wavelet analysis method can achieve a satisfying effect of removing the uneven illumination for digital aerial images and keeping well detail image features, contrast enhancing aim is also achieved
