Global Thresholding


Goal:  To segment an object from the background using thresholding.


            I implemented the following algorithm in matlab.  (See Example 10.10)  Guess the threshold.  Segment

the image using that threshold.  Compute the average intensity of each threshold image.  Set T=1/2*(avg1+avg2).

Repeat segmentation and averaging until T converges.  In the example below, I took the average (107.5) of the

image intensities for the initial guess because the object takes up a considerable portion of the image space.  The

algorithm completed in 3 iterations (with T=127.0).  For this example, it did an excellent job; although, this does

not appear to be a very difficult image to segment.



A) Original image.

B) Segmented image.


matlab code