To detect the image background and to enhance the contrast in grey level images with poor lighting. Some operators to enhance and normalize the contrast in grey level images with poor lighting are introduced. Contrast operators are based on the logarithm function in a similar way to Weber's law. The use of the logarithm function avoids abrupt changes in lighting. Two methodologies are proposed to compute the image background. First, a methodology was introduced to compute an approximation to the background using blocks analysis. This proposal was subsequently extended using mathematical morphology operators. However, a difficulty was detected when the morphological erosion and dilation were employed; therefore, a new proposal to detect the image background was propounded, that is based on the use of morphological connected transformations. That is, the opening by reconstruction is used given its following properties: It passes through regional minima and it merges components of the image without considerably modifying other structures. Opening by reconstruction is employed to define the multibackground notion. Finally, the performance of the proposed operators is illustrated through the processing of images with different backgrounds, the majority of them with poor lighting conditions.
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