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I got really confused by the content of SIFT descriptor. As I got the descriptor should contain the orientation of keypoints. For each keypoint 128 numbers different orientations. And then a feature vector which is histogram of these orientations could be generated. My questions are first after saving the descriptor file I found that the orientations are not more than 150. I saved image with its keypoints using drawKeypoints function and DRAW_RICH_KEYPOINTS as the flag and in documentation it is said that : "For each keypoint the circle around keypoint with keypoint size and orientation will be drawn." In that image I could see some keypoints' orientations look like 300!! Why this is happened? and second the orientations should be in 8 dimensions, is that right? It means I should have just these numbers: 45,90,135, 180, 225, 270, 315 and 360. But I have more than these 8 directions in descriptor! Almost any number between 0 and 150. Why? Does it mean to make a histogram of keypoints I should group all orientations to those 8 groups myself?

Please someone give me an answer, There is a while I am reading about it and still have these issues to understand SIFT completely. Many thanks in advance

Thanks @StevenPuttemans , but the link did not explain that much. I have read more papers and I found that I misundersto

As an answer to my question, for each Keypoints 6 or 7 different parameters were stored. In my case it's 7 parameters in

Hi,

Is it possible to see the dictionary content as visual words from a bow? I found interest points and descriptors of a group of images and clustered them. Now I have a dictionary of visual words which is zero and ones. My question is that is there any way to see the visual words like a piece of image?

Any help would be appreciated.

As an answer to my question, for each Keypoints 6 or 7 different parameters were stored. In my case it's 7 parameters in

As an answer to my question, for each Keypoints 6 or 7 different parameters were stored. In my case it's 7 parameters in

Hi, I have a question regarding BOWKMeansTrainer constructor. Would anyone please tell me what are the parameters of the constructor? I had a look at opencv document, but I could not find any useful information.

So far I know it has these parameters BOWKMeansTrainer::BOWKMeansTrainer(int clusterCount, const TermCriteria& termcrit=TermCriteria(), int attempts=3, int flags=KMEANS_PP_CENTERS ) And I know clusterCount is the dictionary size/number of clusters. I also guess that attempts is the K parameter for K-Mean. It means if it's 3 the trainer will calculate 3-Means/3 steps.

But I want to know what are the rests task?

Many thanks in advance,

Bests,

SIFT Descriptor content I got really confused by the content of SIFT descriptor. As I got the descriptor should contain

What is inside SVM XML classifier file? I made bag of visual words and trained it using SVM. After training I saved clas

What is inside SVM XML classifier file? I made bag of visual words and trained it using SVM. After training I saved clas

What is inside SVM XML classifier file? I made bag of visual words and trained it using SVM. After training I saved clas

Thanks for the comment. Could you explain more about iteration? which iteration you mean? Is this means value from each

BOWKMeansTrainer constructor Hi, I have a question regarding BOWKMeansTrainer constructor. Would anyone please tell me

BOWKMeansTrainer constructor Hi, I have a question regarding BOWKMeansTrainer constructor. Would anyone please tell me

BOWKMeansTrainer constructor Hi, I have a question regarding BOWKMeansTrainer constructor. Would anyone please tell me

Thanks @berak for your time. exactly drawKeypoints() could draw a circle of keypoints. Each circle is a visualizatio

Thanks a lot @berak for the comment I have an xml file of keypoints and descriptors of 93 images. the file looks like t

Thanks a lot @berak for the comment I have an xml file of keypoints and descriptors of 93 images. the file looks like t

Thanks a lot @berak for the comment I have an xml file of keypoints and descriptors of 93 images. the file looks like t

Thanks a lot @berak for the comment I have an xml file of keypoints and descriptors of 93 images. the file looks like t

But I think the picture shows before clustering. I also want to see how they clustered!

I used SIFT to find interest points and descriptor and Kmean to cluster them. Yes exactly like that picture. Is it possi

see the dictionary content from Bag of Words Hi, Is it possible to see the dictionary content as visual words from a bo

If you think I just came here and expect you to ask all my questions it's wrong. I did a lot researching, I could mentio

@berak sorry I don't have a text version of screenshots... No it was not necessary...

So, what's your suggestion to recognize different motions like running, walking, etc?

Haarcascading XML does not work properly I'm pretty new to OpenCV and cascade training. I did train a cascade to recogni

Haarcascading XML does not work properly I'm pretty new to OpenCV and cascade training. I did train a cascade to recogni

@bincos sounds simple... but it could work just for linear movements... like car passing. Do you have any idea for movem

Thanks @bincon for the reply. Exactly, agree with you, but the main problem is here! I don't know how to calculate the

Hi You could use Haar-like feature object detection. have a look at this: https://docs.opencv.org/trunk/dc/d88/tutorial_

Hi @bincos I have the same problem. Please let me know if you have found a solution for the problem and share your exp