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 The threshold values are 0.5216 and 0.2 and normalized to formula_8 for original image and applied white top-hat transform respectively. Top-hat transform In mathematical morphology and digital image processing, top-hat transform is an operation that extracts small elements and details from given images. There exist two types of top-hat transform: The "white top-hat transform" is defined as the difference between the input image and its opening by some structuring element; The "black top-hat transform" is defined dually as the difference between the closing and the input image. Top-hat transforms are used for various image processing tasks, such as feature extraction,