how to recognize pupil using connected components

Assuming pupil is the largest area in an eye image, using the below code, bw=im2bw(i,0.20); [labeled,numObjects] = bwlabel(bw,4); data = regionprops(labeled,'basic'); maxArea = max([data.Area]);

gives me entire eye image.

Answer 1

[Image Analyst]

Then you can't simply use a simple threshold algorithm like you did. You'll need something better. Go here: http://iris.usc.edu/Vision-Notes/bibliography/contents.html to find algorithms you can use.