How can define a object and then find vision.opticalflow of this object?

Dear all: I'm trying to find opticalflow of specific object in movie. How can I define a object and then find opticalflow of this object?

Answer 1

[Image Analyst]

I think you find the optical flow of the whole frame. You can then threshold to find the regions that have higher optical flow (more movement).

[Afsoon]

Thank you for your answer, I mean I want to find optical flow for user-defined region, not all regions with movement. Like set a marker to specific region and then find optical flow for it.