how can i covert rgb image to HSI and separate the intensity component alone

I want to separate intensity components from an rgb image by converting it to HSI space

Answer 1

[KSSV]

https://in.mathworks.com/matlabcentral/fileexchange/13630-rgb-to-hsi-conversion

Read about rgb2hsv

Answer 2

[DGM]

If you just want the intensity (as in HSI) of an image:

ipict = mean(rgbpict,3);

If instead you want value (as in HSV)

vpict = max(rgbpict,[],3);

or if you want lightness (as in HSL)

lpict = min(rgbpict,[],3)/2 + max(rgbpict,[],3)/2;

If you want luma (as in YIQ, YUV, YPbPr, YCbCr, etc)

factors = permute([0.299 0.587 0.114],[1 3 2]); % Rec 470/601 (analog/digital SD video)
%factors = permute([0.2126 0.7152 0.0722],[1 3 2]); % Rec 709 (HDTV video)
ypict = sum(bsxfun(@times,rgbpict,factors),3);

If you want L* lightness (as in CIELAB, CIELUV)

Lpict = rgb2lightness(rgbpict); % introduced in R2019a

otherwise, you can use LAB conversion tools to extract it if you're running something older.