Restauração de iluminação não uniforme em fotografias aéreas coloridas

Abstract

The non-uniform illumination distribution on the negative of aerial photographs can be only done by vignetting or a combination of vignetting with atmospheric factors and bidirectional reflectance. The radiometric degradation that the images present can be corrected by mathematical functions, color balancing methods and histogram manipulation, some of which have already been implemented in commercial programs used in photogrammetry and mapping. However, as the results of this method in use are not always acceptable, there is an interest in developing and perfecting other practical methods that can be used in enterprises. The objective of this work is to show the viability and detailed development for preparation of masks, which are background images that can control and compensate the intensity of non-uniform illumination of photographs. Also the results are discussed in comparison to method of balancing of histograms between adjacent blocks of images that is used in some commercial programs.

Key words: Restoration of images; Vignette; Radiometric degradation.