Top hat top hat is a hard, black silk hat, with fur now often used. The acceptable colors of hats are much as they have traditionally been, with "white" hats (which are actually grey), a daytime racing color, worn at the less formal occasions demanding a top hat, such as Royal Ascot, or with a morning suit. In the U.S. top hats are worn widely in coaching, a driven horse discipline as well as for formal riding to hounds. The collapsible silk opera hat, or "crush hat", is still worn on occasions, and black in color if worn with evening wear as
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