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Image classification using SVM

asked 2016-05-17 09:03:48 -0500

sara1691362 gravatar image

i'm using opencv svm and i want to know if it is possible to know which image is closer to our input image instead of the class which belongs our image.

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this might not be possible.

an SVM does not keep the train data around, all it keeps are the support vectors.

berak gravatar imageberak ( 2016-05-17 10:42:01 -0500 )edit

thank you for your answer. can you please tell me what method can i use to solve this problem?

sara1691362 gravatar imagesara1691362 ( 2016-05-17 12:50:26 -0500 )edit
2

it's not an answer (so far)

an SVM does classification , but your question hints, that you want something slightly different, like finding the 'closest neighbour' ? a simple 'nearest neighbour search' (e.g. comparing all of your train samples to the test one using norm(a,b), and keeping the one with lowest score) would do that, also there's flann::Index

berak gravatar imageberak ( 2016-05-17 13:01:13 -0500 )edit

is there a possible way to get the closest neighbour + the class which belongs the image (using the nearest neighbour ) ?

sara1691362 gravatar imagesara1691362 ( 2016-05-17 16:33:09 -0500 )edit
1

sidenote: do you really need the closest image ? or would any image from the predicted class do?

berak gravatar imageberak ( 2016-05-18 02:14:37 -0500 )edit

i need the closest image + which class it belongs

sara1691362 gravatar imagesara1691362 ( 2016-05-18 04:56:16 -0500 )edit

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answered 2016-05-18 02:11:05 -0500

berak gravatar image

updated 2016-05-18 02:12:22 -0500

so, here is a simple nearest neighbour classification.

(you'll find though, that it is less accurate, than an SVM or ANN_MLP):

void nearest(const cv::Mat &testData, const vector<cv::Mat> &trainData, int &best, double &mind)
{
    mind=DBL_MAX;
    best = -1;
    for (size_t r=0; r<trainData.size(); r++)
    {
        double d = norm(testData, trainData[r]);
        if (d < mind)
        {
            mind = d;
            best = r;
        }
    }
}

vector<Mat> trainData = ... 
vector<int> trainLabels = ...

Mat testData = ...
int best;
double dist;

nearest(testData, trainData, best, dist);

int predicted = trainLabels[best];
Mat closest = trainData[best];
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I am currently working on a project where I have to extract the facial expression from a video. I've extracted the landmarks, now i want to classify the emotions + get the closest image's landmarks. So is there a possibility to do the classification based on the facial landmarks?

sara1691362 gravatar imagesara1691362 ( 2016-05-18 05:53:07 -0500 )edit
1

sure, just put your landmarks into a Mat

berak gravatar imageberak ( 2016-05-18 06:43:47 -0500 )edit

can you please tell me how can i do that?

sara1691362 gravatar imagesara1691362 ( 2016-05-18 06:44:39 -0500 )edit
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Asked: 2016-05-17 09:03:48 -0500

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Last updated: May 18 '16