How do I threshold only a certain portion of an image?

I am trying to find the coordinates of something in an image. For example, I have to find any image on google, select a point of interest and find the coordinates of it. For my first example I am using a baseball player throwing a baseball. I converted to gray scale and threshold to only show the white portions of the image. Although, the baseball players pants are getting into the picture along with the baseball. Is there any way I am able to only threshold where the baseball is at or something to just find the point of interest I am looking for. I have only been using Matlab for about a week. Therefore, please try and break the answer down to a dummy language where I can understand, lol. Thank you for the help.

Answer 1

[Image Analyst]

See my Image Segmentation Tutorial. http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862

If the baseball is the same intensity as other pixels in the image then you're going to have to look at other things to extract only the baseball, such as area or circularity.

[Alexander Killam]

I do not understand exactly how to do this by looking at the program itself. I need something basic please

[Image Analyst]

That is basic - basic code with a basic, simple image. But you're not asking to do something basic. Do you think that some 5 or 10 line chunk of code is going to be able to find any baseball in any image? It's not going to happen.

[Alexander Killam]

You are right. i am just trying to learn from Matlab all on my own without any experience. May be going a little to advanced for what I know. Thank you.

[Dishant Arora]

To understand the program better set breakpoint in the code, go through the code line by line, step in to the functions to learn more about functions called.

And it'd be better if you have some prior knowledge of image processing before directly jumping into MATLAB. You can refer to Digital Image Processing/Digital Image Processing using MATLAB by Gonzalez to start with.