Thursday, August 25, 2011

Review and what needs to be done - Biometric Face recognition system

We talked about haar training in the previous post. Let's see how far we have come till date

1. Installed opencv
2. Did some good exercises related to openCV intro programming
3. Created eye and face detectors using haar cascade classifiers
4. Learnt how to create an xml file with haar training that can be used to create an object detector

Now let's divulge into our main topic of biometric face recognition. In one of my previous posts, I told you about Biometric face recognition, it's significance and the contests related to it.

The reason I made you learn the creating of face detector due to the fact that the first step in face recognition is detecting the face in a back ground, like the one  shown below

Detecting face is just the beginning. The next step is to normalise the face, so that only the face part is cut. Then we will apply histogram equilisation to make the face invariant to brightness and contrast. Finally, we rotate the face, so that the eye coordinates remain on same height. This is needed, since we will be comparing photos for face recognition and if the guy tilts the head, his nose may be taken as one of the eyes, by mistake by the recognition system. In the end, the piece that we actually need looks like this

The face recognition system compares this face, with the faces like this to recognise people. Incidentally, there is a savior for us. It's the CSU face evaluation system. Just google for the name and download the zipped file. The beauty of CSU face evaluation system is that, you supply the image containing face, along with any back ground, with the eye center coordinates, and it returns you the face which is detected, normalised, equalised and rotated.

The only thing, that we need to supply it, is the eye center coordinates of the image i.e., the x and y coordinates of left eye center (eye ball center) and the same of the right eye. To get these coordinates, I used the eye detector, which I made you learn in the previous posts. Since, it draws a square around the eye, finding the center of that square is no big task. Will explain it to you in future posts, and the next post will be on sunday ( 28/08/11). For now, just download the CSU face evaluation system and try to decipher and also carefully go through it's documentation.

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