Revision history [back]

What you want is the maxima and minima of the shape. Use something like this, with one scan of the image.

int x_min = img.cols, x_max = 0, y_min = img.rows, y_max = 0;
int r, c;
for( r = 0 ; r < img.rows ; ++r )
{
    for( c = 0 ; c < img.cols ; ++c )
    {
        if( img.at< uchar >( r, c ) == 255 )
        {
            if( r < y_min )
                y_min = r;
            if( r > y_max )
                y_max = r;
            if( c < x_min )
                x_min = c;
            if( c > x_max )
                x_max = c;
        }
    }
}
cv::Point middle( (int)((x_max - x_min)/2), (int)((y_max-y_min)/2) );

If you are more interested by the center of gravity of silhouette, try this sample, which draw the center with a circle, using the moment and findcontours (that you probably already used to detect your silhouette?)

What you want is the maxima and minima of the shape. Use something like this, with one scan of the image.

int x_min = img.cols, x_max = 0, y_min = img.rows, y_max = 0;
int r, c;
for( r = 0 ; r < img.rows ; ++r )
{
    for( c = 0 ; c < img.cols ; ++c )
    {
        if( img.at< uchar >( r, c ) == 255 )
        {
            if( r < y_min )
                y_min = r;
            if( r > y_max )
                y_max = r;
            if( c < x_min )
                x_min = c;
            if( c > x_max )
                x_max = c;
        }
    }
}
cv::Point middle( (int)((x_max (int)(x_min+(x_max - x_min)/2), (int)((y_max-y_min)/2) (int)(y_min+(y_max-y_min)/2) );

If you are more interested by the center of gravity of silhouette, try this sample, which draw the center with a circle, using the moment and findcontours (that you probably already used to detect your silhouette?)