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To save vector "KeyPoint" to file using builtin write function

asked 2012-11-11 09:47:35 -0500

ipunished gravatar image


I want to write a vector of detected Keypoints to file and while I was told it can be done through operator overloading, I found out a function in the keypoint class documentation.

The documentation here shows a function called write..

// reading/writing a vector of keypoints to a file storage
void write(FileStorage& fs, const string& name, const vector<KeyPoint>& keypoints);
void read(const FileNode& node, vector<KeyPoint>& keypoints);

So basically there is a function to write the vector to file.. can some one please explain this and also, an example on how to use this would be great.

Thank you

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answered 2012-11-11 10:15:38 -0500

Simone gravatar image

updated 2012-11-11 10:19:25 -0500


it's actually simple. In order to save your keypoints

 vector<Keypoint> mykpts;
 FileStorage fs("keypoints.yml", FileStorage::WRITE);
 write( fs , "aNameYouLike", mykpts );

This will store your keypoints in a file named keypoints.yml and the node containing the data is named "aNameYouLike". This will be used to read back the keypoints from the file:

  vector<Keypoint> mykpts2;
  FileStorage fs2("keypoints.yml", FileStorage::READ);
  FileNode kptFileNode = fs2["aNameYouLike"];
  read( kptFileNode, mykpts2 );

You may want to check the XML/YAML file storage documentation for more information.

Hope it helps


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Thank you. That was very helpful. I wish I could upvote this more than once.

ipunished gravatar imageipunished ( 2012-11-11 10:38:51 -0500 )edit

thank you very much too! the information was very useful

Olbitla gravatar imageOlbitla ( 2012-12-05 13:39:01 -0500 )edit

i am using XML storage way.It can save keypoint perfectly of first image. now i want that i used for loop and it save my image keypoint one by how can i do it.

salman gravatar imagesalman ( 2017-10-13 08:58:14 -0500 )edit
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Asked: 2012-11-11 09:47:35 -0500

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Last updated: Nov 11 '12