Opera hat Opera hat An opera hat, also called a chapeau claque or gibus, is a top hat variant that is collapsible through a spring system, originally intended for less spacious venues, such as theatre and opera visits. Typically made of satin in black colour, its advantage is that it folds vertically through a push or a snap on the top of the hat, in order to be conveniently stored in a wardrobe or under the seat. Invertably, it opens in the same one moment fashion by an easy push from underneath. Its French name "chapeau claque" is a composition of "chapeau",
Top-hat transform controlled by the choice of the structuring element formula_7. The bigger the latter, the larger the elements extracted. Both top-hat transforms are images that contain only non-negative values at all pixels. One of its most important uses in image segmentation is to adjust nonuniform lighting conditions on an image and provide a better threshold value for separating objects. Assume we are only interested in small blobs on the image and we want to remove the larger bright objects. In this case, the white top-hat transform can remove larger bright objects and retain small blobs by selecting the size of the