Get HOG image features from OpenCV + Python?

Question

I\'ve read this post about how to use OpenCV\'s HOG-based pedestrian detector: How can I detect and track people using OpenCV?

I want to use HOG for detecting othe

Answer 1

I would disagree with the argument of peakxu. The HOG detector in the end is "just" a rigid linear filter. any degrees of freedom in the "object" (i.e. persons) lead to bluring in the detector, and are not actually handled by it. There is an extension of this detector using latent SVMs that does explicitly handle dgrees of freedom by introducing structural constraints between independent parts (i.e. head, arms, etc) as well as allowing for multiple appearances per object (i.e. frontal people and sideways people...).

Regarding the HOG detector in opencv: In theory you can upload another detector to be used with the features, but you cannot afaik get the features themselves. thus, if you have a trained detector (i.e. a class specific linear filter) you should be able to upload that into the detector to get the fast detections performance of opencv. that said it should be easy to hack the opencv source code to provide this access and propose this patch back to the maintainers.