Hat box collapsible version for evenings, known as a gibus. They might also include storage space for items such as a hat brush. Designs became quite large during the Victorian era. A letter to "The Times" in 1844 warned travellers that Blackwall Railway's porters had charged a 1d to carry a hat box onto the train and a further 6d for transporting it to the London terminus, with the traveller himself paying only 4d for the journey. He recommended that travellers with luggage should go by steamboat. While traditionally hat boxes are circular or square in shape, some versions may follow the
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