How do i calculte Threshold size?

Hi, im doing some road sign detection with matlab and one of the step i need to do is to detect the blob by threshold size? What does that mean? Im working right now in HSV. How can i tell my program to detect ROI (Blob) with Threshold size? Thanx!

Answer 1

[Shashank Prasanna]

It just means how strictly are you going to qualify your blob. Are you going to say this maybe is it, or no, it has to be perfect else i am not considering it.

The following link should help you set your thresholds: http://www.mathworks.com/help/vision/ref/detectsurffeatures.html

[Simon Dussault]

Is there another way of doing it without this function? cause i dont hace computer vision system toolbox.

[Shashank Prasanna]

Maybe this is helpful:

http://www.mathworks.com/matlabcentral/fileexchange/28300-opensurf-including-image-warp

its available in file exchange but does the same thing

Answer 2

[Image Analyst]

Simon, you already marked this as "Accepted" so you probably don't need help anymore. But for other people, if you want to see how you can threshold blobs based on size, you can check out the Image Segmentation Tutorial in my File Exchange: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862 There I pick out two classes of coins, dimes and nickels (10 and 5 cent coins), from an image of mixed coins by thresholding based on size.

[Simon Dussault]

Thx image analyst! :D