How to do preprocessing and post processing for Watershed Segmentation of an image?

Hello, I need to perform watershed segmentation on image 'step1.jpg' and the expected result is image 'watershedOutput.jpg'. I got the information that watershed segmentation need pre-processing image and past-processing image .my doubt is What are the pre-processing and post-processing function to be done for getting the expected output?

Could you kindly help for doing the same?

This is for detecting the unfocused raindrops in the input image. I got the gradient image as mentioned in the attached image with sobel operator.

Thank You. Simi

Answer 1

[SIMI PS]

I forgot to attach the images as mentioned in my question. Please find the same here.