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k mean clustering of hsv histogram of frames of a video

asked 2013-10-28 12:44:49 -0500

zulfiqar gravatar image

updated 2013-10-28 13:18:19 -0500

berak gravatar image

I have calculated the hsv histogram of frames of a video . now i want to cluster frames in using k mean clustering i have searched it and found the in build method

kmeans(InputArray data, int K, InputOutputArray bestLabels, TermCriteria criteria, int attempts, int flags, OutputArray centers=noArray() )

but I don't understand how to use it can anyone explain it. my code is shown below if anyone can tell what i have to pass as arguments

// Set up images
System::String ^ str = path->Text ;
char* str2 = (char*)Marshal::StringToHGlobalAnsi(str).ToPointer();
printf(str2);

String^ P = path->Text;
//const char* t = P.
IplImage* img = cvLoadImage(str2);
IplImage* back_img = cvCreateImage( cvGetSize( img ), IPL_DEPTH_8U, 1 );

// Compute HSV image and separate into colors
IplImage* hsv = cvCreateImage( cvGetSize(img), IPL_DEPTH_8U, 3 );
cvCvtColor( img, hsv, CV_BGR2HSV );

IplImage* h_plane = cvCreateImage( cvGetSize( img ), 8, 1 );
IplImage* s_plane = cvCreateImage( cvGetSize( img ), 8, 1 );
IplImage* v_plane = cvCreateImage( cvGetSize( img ), 8, 1 );
IplImage* planes[] = { h_plane, s_plane };
cvCvtPixToPlane( hsv, h_plane, s_plane, v_plane, 0 );

// Build and fill the histogram int h_bins = 30, s_bins = 32; CvHistogram* hist; { int hist_size[] = { h_bins, s_bins }; float h_ranges[] = { 0, 180 }; float s_ranges[] = { 0, 255 }; float* ranges[] = { h_ranges, s_ranges }; hist = cvCreateHist( 2, hist_size, CV_HIST_ARRAY, ranges, 1 ); } cvCalcHist( planes, hist, 0, 0 ); // Compute histogram //cvNormalizeHist( hist, 20*255 ); // Normalize it

//cvCalcBackProject( planes, back_img, hist );// Calculate back projection
//cvNormalizeHist( hist, 1.0 ); // Normalize it

// Create an image to visualize the histogram
int scale = 10;
IplImage* hist_img = cvCreateImage( cvSize( h_bins * scale, s_bins * scale ), 8, 3 );
cvZero ( hist_img );

// populate the visualization
float max_value = 0;
cvGetMinMaxHistValue( hist, 0, &max_value, 0, 0 );

for( int h = 0; h < h_bins; h++ ){
    for( int s = 0; s < s_bins; s++ ){
        float bin_val = cvQueryHistValue_2D( hist, h, s );
        int intensity = cvRound( bin_val * 255 / max_value );
        cvRectangle( hist_img, cvPoint( h*scale, s*scale ),
                    cvPoint( (h+1)*scale - 1, (s+1)*scale - 1 ),
                    CV_RGB( intensity, intensity, intensity ),
                    CV_FILLED );
    }
}

// Show original
cvNamedWindow( "Source", 1) ;
cvShowImage( "Source", img );

// Show back projection
//cvNamedWindow( "Back Projection", 1) ;
//cvShowImage( "Back Projection", back_img );

// Show histogram equalized
cvNamedWindow( "H-S Histogram", 1) ;
cvShowImage( "H-S Histogram", hist_img );

cvWaitKey(0);

cvReleaseImage( &img );
cvReleaseImage( &back_img );
cvReleaseImage( &hist_img );

     }
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answered 2013-10-28 13:10:46 -0500

stereomatching gravatar image

updated 2013-10-28 13:49:37 -0500

The first question I would like to ask you is why do you still using outdated, deprecated, old-style c api?If there is no specific reason, then please use the c++ interface, which has a better support for the moment. The codes written by c++ api are much more easier to read and maintain, prefer c++ api should save you and your colleagues a lot of headaches.

About your problem, you need to map the original data to a group of data(samples), remap the labels and centers generated by kmeans algorithm back to the image.

cv::Mat src = cv::imread(Folder + "perspective05.jpg");
if(src.empty()){
    std::cerr<"can't read the image"<std::endl;
    return -1;
}

//step 1 : map the src to the samples
cv::Mat samples(src.total(), 3, CV_32F);
float *samples_ptr = samples.ptr<float>(0);
for( int row = 0; row != src.rows; ++row){
    uchar *src_begin = src.ptr<uchar>(row);
    uchar *src_end = src_begin + src.cols * src.channels();        
    while(src_begin != src_end){
        samples_ptr[0] = src_begin[0];
        samples_ptr[1] = src_begin[1];
        samples_ptr[2] = src_begin[2];
        samples_ptr += 3; src_begin +=3;
    }        
}

//step 2 : apply kmeans to find labels and centers
int clusterCount = 3;
cv::Mat labels;
int attempts = 5;
cv::Mat centers;
cv::kmeans(samples, clusterCount, labels,
           cv::TermCriteria(CV_TERMCRIT_ITER | CV_TERMCRIT_EPS, 
                            10, 0.01),
           attempts, cv::KMEANS_PP_CENTERS, centers);

//step 3 : map the centers to the output
cv::Mat new_image(src.size(), src.type());
for( int row = 0; row != src.rows; ++row){
    uchar *new_image_begin = new_image.ptr<uchar>(row);
    uchar *new_image_end = new_image_begin + new_image.cols * 3;
    int *labels_ptr = labels.ptr<int>(row * src.cols);

    while(new_image_begin != new_image_end){
        int const cluster_idx = *labels_ptr;
        float *centers_ptr = centers.ptr<float>(cluster_idx);
        new_image_begin[0] = centers_ptr[0];
        new_image_begin[1] = centers_ptr[1];
        new_image_begin[2] = centers_ptr[2];
        new_image_begin += 3; ++labels_ptr;
    }
}

This blog show you the whole process, explain the reasons and encapsulate those annoying details under the hood.

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Comments

auto probably won't work with managed c++ (winforms, again)

nice blog ;)

berak gravatar imageberak ( 2013-10-28 13:15:31 -0500 )edit

@berak thanks. My bad, I haven't tried managed c++ before(never find a need for garbage collection since c++ support RAII + Qt do a good job on gui development).I change the auto back to explicit type.

stereomatching gravatar imagestereomatching ( 2013-10-28 13:45:15 -0500 )edit

how can i make sample of multiple images?

zulfiqar gravatar imagezulfiqar ( 2013-10-29 10:50:03 -0500 )edit

Hi the code im currently writing is doing something similar to this, should be done in 2 weeks in case you find it useful. Also i know it's messy ect.. will optimise it when i have everything working.. https://github.com/albertJ32/MR8-Filt...

albertJ gravatar imagealbertJ ( 2015-07-24 08:30:16 -0500 )edit
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Asked: 2013-10-28 12:44:49 -0500

Seen: 3,481 times

Last updated: Oct 28 '13