> I want to create program that detect the orange ball automatically with sliding window method, but I don't know how to do it. Can somebody instuct me how to do it?
Welcome to the forum, @Krittanai. The Answers forum is a great place to get un-stuck when solving problems using MATLAB but your question has a much wider scope. Your question is about how to do an entire project and you seems to be in the learning and discovering phase. After you learn more about object detection using sliding windows and when you start to implement this in MATLAB, this is the best place to ask specific questions.
In the mean time, there are books, articles, blogs, and other forums that might be helpful. For example, I found this link below after search for less time than it took me to write this :)
As for your code, you are reading in the image correctly and displaying the rectangle correctly but remember that you don't need to display the image to do computations on the image. However, you'll definitely want to plot the image and the rectangle at then end after your algorithm identifies the object.
