http://docs.opencv.org/trunk/modules/... What does the grid_x and grid_y means ? Suppose I use radius = 2. How can I calculate the neighbor, gird_x, and grid_y?
'radius' is the distance from the center pixel to the neighbours, 'neighbours' is their count, like here:
with lbph, the face region gets divided into seperate patches, like this:
grid_x and grid_y are the number of patches in x and y direction (8 in this case, like the default with opencv)
for each patch, a separate (2^neighbours bins)histogram is calculated, and later concatenated to a
grid_x * grid_y * (2^neighbours) element feature vector.
(you can already see, that increasing the neighbours count will be very expensive)
[images taken from : Face Recognition with Local Binary Patterns, Timo Ahonen, Abdenour Hadid, and Matti Pietikäinen - you might want to read this..]
Since my discussion is long. Comment box is not a good choice.
@berak Thank you for your explaination. I just got an article from Jayso. http://www.answers.opencv.org/questio...
Is your given picture is 7x7 not 8x8?
Let me confirm my understanding from your post. It means grid_x and grid_y are arbitrary value that we can put? But do not put patch size smaller than radius.
"Is your given picture is 7x7 not 8x8?" - hehe, right. i can't count ;)
hmm, yes, grid_x and grid_y are somewhat arbitrary. just remember, that you're filling a 256 bin histogram per patch, so if you have a lot of (small) patches, those histograms will get very sparse. for a 80x80 img, and a 8x8 grid, you got 10x10=100pixels per patch.
also, the more smaller the grid gets, the more patches, and the longer the resulting feature vector.
do your own experiments there !
good papers in the other answer, btw, - read them ;)
Asked: 2015-02-17 04:08:48 -0600
Seen: 655 times
Last updated: Feb 28 '15
