separating pixels and calculating number of pixels

i have to calcuate how many number of pixels present in selected area

iam done the priject that i need to calcuate precition and accuarcy so i need to extract the number of pixcels that are presented in my required area

it is possible to extract number of pixel

[Mehmed Saad]

https://ch.mathworks.com/matlabcentral/answers/66552-how-to-get-number-of-pixels-of-red-color-in-an-image#answer_78214

[Image Analyst]

How are you defining the area? Some mask gotten from thresholding, or manually tracing using drawpoints()?

[krishna kotha]

1st iam seperating the area of pixel by using thresholding value then again iam considering vertial and horizintal lenth of area pixels to get exact required area of pixels. So i need these number of pixels values in each indiviual steps. how it is possible.