Scale dependent signal representations have proved to be useful in several image processing applications. In this paper, we define a toggle operator for binarization/ segmentation purposes based on scaled versions of an image transformed by morphological operations. The toggle decision rule, determining the new value of a pixel, considers local spatial information, in contrast to other multiscale approaches that takes into account mainly global information (e.g., the scale signal under study). We show that the proposed operator can identify significant image extrema information in such a way that when it is used in a binarization process yields very good segmentation and filtering results. Our algorithm is validated against known threshold-based segmentation methods using images of different classes and subjected to different lighting conditions.