How to use Principal component Analysis(PCA) to extract feature from images How can use principal component Analysis to extract feature from image that is been acquired by the camera?
PCA is mostly used to reduce the dimensionality of the features. 

You should first use a feature detector before you can use PCA to reduce the dimensions of these features. Common feature detectors are SIFT, SURF, ORB etc. Some of them are even available in OpenCV.