This function is the white top hat (also called top hat). In mathematical morphology and digital image processing,
top-hat transform is an operation that extracts small elements and details from given images.
The white top-hat transform is defined as the difference between the input image and its opening by some structuring element.
Top-hat transforms are used for various image processing tasks, such as feature extraction, background equalization, image enhancement, and others. (Wikipedia)
This function is the white top hat (also called top hat). In mathematical morphology and digital image processing, top-hat transform is an operation that extracts small elements and details from given images. The white top-hat transform is defined as the difference between the input image and its opening by some structuring element. Top-hat transforms are used for various image processing tasks, such as feature extraction, background equalization, image enhancement, and others. (Wikipedia)
See
http://docs.opencv.org/2.4/doc/tutorials/imgproc/opening_closing_hats/opening_closing_hats.html
Param: image
Image to process.
Param: options
Top hat options.
Returns
The top-hatted image.