Opera hat which means hat, and "claque", which means "tap" or "click". The "chapeau claque" is thus a hat that folds with a click, and unfolds likewise. In English the hat model is usually referred to as a "collapsible top-hat", "gibus" or more often "opera hat"- The construction may originally have been inspired by an historical hat model called "chapeau bras" ("arm hat"), made as bicorne or tricorne to be carried folded under the arm On May 5, 1812, a London hatter called Thomas Francis Dollman patented a design for "an elastic round hat" supported by ribs and springs. His patent was
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