top- hat transform for signal processing

Hello, I want to know how to write matlab code for top-hat and bottom-hat (morphological operation) for signal processing??

Answer 1

[Image Analyst]

I know imtophat() and imbothat() should work for 1-D signals. They're in the Image Processing Toolbox. Observe:

v = randi(20, 1, 15)

v = 1×15

14 18 16 5 9 7 5 20 18 17 14 2 1 19 1

windowWidth = 3;
v2 = imtophat(v, true(1, windowWidth))

v2 = 1×15

0 4 2 0 4 2 0 3 1 0 0 0 0 18 0

Answer 2

[DGM]

The tophat and bottomhat operations are the difference of the source image and the opening/closing of said image with the selected strel. They represent the changes made -- i.e. the objects removed by opening or the holes filled by closing.

If you're trying to write your own, then:

For binary data, they should be equivalent to

outpict = inpict & ~imopen(inpict,se); % tophat
outpict = ~inpict & imclose(inpict,se); % bothat

For numeric data, they are

outpict = inpict - imopen(inpict,se); % tophat
outpict = imclose(inpict,se) - inpict; % bothat

The same should apply for 1D cases. Ultimately, opening and closing operations can be further reduced to a set of routines based on a simple moving-window maximum filter.

[Image Analyst]

Of course if they have imopen() then they have the Image Processing Toolbox and can call imtophat() directly. I think you might have meant to use movmin() and movmax() which do not require the Image Processing Toolbox.

[DGM]

movmax could be used in the 1D case, but I intentionally was trying to speak generally. To that end, it's worth noting that movmax() is something that I still consider relatively new (though I guess it's in OP's version).

Yes, it's reasonable to assume the availability of included tools once IPT is being used, but I had to consider two things. I don't know if this is just another "how do I reinvent the wheel for my homework problem" question. Additionally, I didn't want to pseudocode something using generic function names like "open()" or "close()" knowing that someone would actually copy and paste them and run them blind.