sample bgfg_segm.cpp don't display background in 2.1.0 version (Bug #317)

i had the same problem

The following function fills model->background image when model is MOG (cvCreateGaussianBGModel). I hope this helps those who encounter this problem in the meanwhile.

 1typedef struct [[MyCvGaussBGValues]]
 2{
 3    float match_sum;
 4    float weight;
 5    float meanr3;
 6    float variancer3;
 7}
 8[[MyCvGaussBGValues]];
 9
10static void updateBackground(CvGaussBGModel* bg_model)
11{
12    int K = bg_model->params.n_gauss;
13    int nchannels = bg_model->background->nChannels;
14    int height = bg_model->background->height;
15    int width = bg_model->background->width;
16    MyCvGaussBGValues *g_point = (MyCvGaussBGValues *) ((CvMat*)(bg_model->g_point))->data.ptr;
17    MyCvGaussBGValues *mptr = g_point;
18
19    for(int y=0; y<height; y++)
20    {
21        for (int x=0; x<width; x++, mptr+=K)
22        {
23            int pos = bg_model->background->widthStep*y + x*nchannels;
24            float meanr3 = {0.0, 0.0, 0.0};
25
26            for(int k=0; k<K; k++)
27            {
28                for(int m=0; m<nchannels; m++)
29                {
30                    mean[m] += mptr[k].weight * mptr[k].mean[m];
31                }
32            }
33
34            for(int m=0; m<nchannels; m++)
35            {
36                bg_model->background->imageData[pos+m] = (uchar) (mean[m]+0.5);
37            }
38        }
39    }
40}
41

Call just after cvUpdateBGStatModel(), as this:

1cvUpdateBGStatModel( tmp_frame, bg_model, update_bg_model ? -1 : 0 );
2updateBackground((CvGaussBGModel*)bg_model);

Note: works only for 3-channels images.

Improved previous version. Anyone here?

  1typedef struct [[MixData]]1
  2{
  3    float match_sum;
  4    float weight;
  5    float mean;
  6    float variance;
  7}
  8[[MixData]]1;
  9
 10typedef struct [[MixData]]3
 11{
 12    float match_sum;
 13    float weight;
 14    float meanr3;
 15    float variancer3;
 16}
 17[[MixData]]3;
 18
 19void [[BackgroundThread]]::update8uC1(CvGaussBGModel* bg_model)
 20{
 21    int K = bg_model->params.n_gauss;
 22    float T = bg_model->params.bg_threshold;
 23    int height = bg_model->background->height;
 24    int width = bg_model->background->width;
 25    MixData1 *g_point = (MixData1 *) ((CvMat*)(bg_model->g_point))->data.ptr;
 26    MixData1 *mptr = g_point;
 27
 28    for(int y=0; y<height; y++)
 29    {
 30        for (int x=0; x<width; x++, mptr+=K)
 31        {
 32            int pos = bg_model->background->widthStep*y + x;
 33            float mean = 0.0;
 34            float wsum = 0.0;
 35            int kForeground = K;
 36
 37            for(int k=0; k<K; k++)
 38            {
 39                wsum += mptr[k].weight;
 40                if (wsum > T)
 41                {
 42                    kForeground = k+1;
 43                    break;
 44                }
 45            }
 46
 47            for(int k=0; k<kForeground; k++)
 48            {
 49                mean += mptr[k].weight * mptr[k].mean;
 50            }
 51
 52            bg_model->background->imageData[pos] = (uchar) (mean/wsum);
 53        }
 54    }
 55}
 56
 57void [[BackgroundThread]]::update8uC3(CvGaussBGModel* bg_model)
 58{
 59    int K = bg_model->params.n_gauss;
 60    float T = bg_model->params.bg_threshold;
 61    int nchannels = bg_model->background->nChannels;
 62    int height = bg_model->background->height;
 63    int width = bg_model->background->width;
 64    MixData3 *g_point = (MixData3 *) ((CvMat*)(bg_model->g_point))->data.ptr;
 65    MixData3 *mptr = g_point;
 66
 67    for(int y=0; y<height; y++)
 68    {
 69        for (int x=0; x<width; x++, mptr+=K)
 70        {
 71            int pos = bg_model->background->widthStep*y + x*nchannels;
 72            float meanr3 = {0.0, 0.0, 0.0};
 73            float wsum = 0.0;
 74            int kForeground = K;
 75
 76            for(int k=0; k<K; k++)
 77            {
 78                wsum += mptr[k].weight;
 79                if (wsum > T)
 80                {
 81                    kForeground = k+1;
 82                    break;
 83                }
 84            }
 85
 86            for(int k=0; k<kForeground; k++)
 87            {
 88                for(int m=0; m<nchannels; m++)
 89                {
 90                    mean[m] += mptr[k].weight * mptr[k].mean[m];
 91                }
 92            }
 93
 94            for(int m=0; m<nchannels; m++)
 95            {
 96                bg_model->background->imageData[pos+m] = (uchar) (mean[m]/wsum); //+0.5
 97            }
 98        }
 99    }
100}
101

Call just after cvUpdateBGStatModel(), as this:

1cvUpdateBGStatModel(image, model, -1);
2update8uC3((CvGaussBGModel*)model);

Where to use this code i.e in which lib?