How to extract SURF features on specific parts on facial images

Hello, I'm doing a project on matching sketches with photos. I'm using SURF descriptor for feature extraction from facial image. those resultant features are used for classification.But surf descriptor extracts the features on whole image. I want to extract features from specific points like eye corner, nose tip, mouth etc. How to select those points on the facial image and do extraction...Please help me out

Thank you

[KSSV]

An example image will help better to understand the problem.

[KDR]

Hi Kssv, i have given an example image

[KSSV]

Have you seen this?

https://in.mathworks.com/matlabcentral/fileexchange/36855-face-parts-detection

[KDR]

Thank you sir.. Main intension here is matching sketches to photo.Previously i had used surf descriptor on whole image and its features one row per image is used for classification ie without preprocessing the feature extraction, there i didn't get positive result. so can i apply feature extraction on these facial parts for getting a proper match. Sir please, any suggestion regarding how can i proceed with it..

Answer 1

[Image Analyst]

What if you just mask out the part of the image you don't care about, like if you use a binary image

grayImage(mask) = 250; % Or whatever white value you want to erase the image.