Opera hat characteristic snapping sound heard upon opening a gibus suggested a third name, the "chapeau claque", "claque" being the French word for "slap". 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
Top-hat transform grid "E" (such as "R" or "Z") into the real line. Let formula_2 be a grayscale structuring element. Then, the white top-hat transform of "f" is given by: where formula_4 denotes the opening operation. The black top-hat transform of "f" (sometimes called the "bottom-hat" transform ) is given by: where formula_6 is the closing operation. The white top-hat transform returns an image, containing those "objects" or "elements" of an input image that: The black top-hat returns an image, containing the "objects" or "elements" that: The size, or width, of the elements that are extracted by the top-hat transforms can be