1

What is the meaning of gamma normalization in HOG(Histogram of Gradients)? Is it the same as gamma correction? Because I came across many journals saying that gamma normalization in HOG is the square root of the image intensity. But it is different compared to gamma correction's formula.

Jeru Luke
  • 20,118
  • 13
  • 80
  • 87
toechfah
  • 11
  • 3
  • Possible duplicate of [gamma correction in opencv hog.cpp](http://stackoverflow.com/questions/16593126/gamma-correction-in-opencv-hog-cpp) – NoDataDumpNoContribution Jan 06 '17 at 15:55
  • @toechfah You either mean **Gamma correction** or **Normalization**. I have not come across something called 'Gamma Normalization'. If **gamma correction** is what you are looking for you check [THIS ANSWER](http://stackoverflow.com/questions/33322488/how-to-change-image-illumination-in-opencv-python/41061351#41061351). – Jeru Luke Jan 06 '17 at 17:37
  • **Normalziation** is carried out in Histogram of Gradients (HOG). Please check [THIS POST](https://www.learnopencv.com/histogram-of-oriented-gradients/). The author explains something called **Block Normalization**. Hope this helps. – Jeru Luke Jan 06 '17 at 17:39
  • @JeruLuke thanks for editing and answering my question – toechfah Jan 09 '17 at 06:00

1 Answers1

0

Gamma Normalization in HOG is actually Power Law Transformation

s = cr^γ

where s is output pixel, r is input pixel, c is constant and γ is exponent. Different devices used for image capture, display and printing use this power law transformation to correct image intensity values and this process is known as gamma correction. In short, gamma normalization in HOG is same as gamma correction.

TheEsnSiavashi
  • 1,245
  • 1
  • 14
  • 29
user8190410
  • 1,264
  • 2
  • 8
  • 15