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Minimum bounding box

In geometry, the minimum or smallest bounding or enclosing box for a point set S in N dimensions is the box with the smallest measure (area, volume, or hypervolume in higher dimensions) within which all the points lie. When other kinds of measure are used, the minimum box is usually called accordingly, e.g., "minimum-perimeter bounding box".

The minimum bounding box of a point set is the same as the minimum bounding box of its convex hull, a fact which may be used heuristically to speed up computation.

The terms "box" and "hyperrectangle" come from their usage in the Cartesian coordinate system, where they are indeed visualized as a rectangle (two-dimensional case), rectangular parallelepiped (three-dimensional case), etc.

In the two-dimensional case it is called the minimum bounding rectangle.

경계 상자 그리기 샘플 

#define bh_red Scalar(0,0,255)
#define bh_green Scalar(0,255,0)
#define bh_blue Scalar(255,0,0)
#define bh_yellow Scalar(0,255,255)

void bhDrawColorLabel(Mat src,string title,Scalar color, int pos,int size=20)
{
    int lineSize = 20;
    Point offset( 10,10);
    int position = pos * size;
    line(src,Point(offset.x,position+offset.y),Point(offset.x+lineSize,position+offset.y),color);
    putText(src,title,Point(offset.x+lineSize,position+10),CV_FONT_HERSHEY_COMPLEX,0.4,Scalar(255,255,255));
}

int main( int argc, char *argv[] )  
{  

Mat image; Mat image_gray; Mat image_gray2; Mat threshold_output;
int thresh=100, max_thresh=255;


//Load Image
//image =imread(argv[1]);
image_gray =imread("c:\\test100.bmp",0);


blur( image_gray, 
    image_gray2,
    Size(3,3) );
//Threshold Gray&Blur Image
threshold(image_gray2, 
    threshold_output, 
    thresh, 
    max_thresh, 
    THRESH_BINARY);

//2D Container
vector<vector<Point>> contours;

//Fnd Countours Points, (Imput Image, Storage, Mode1, Mode2, Offset??)
findContours(threshold_output,
    contours, // a vector of contours
    CV_RETR_EXTERNAL,// retrieve the external contours
    CV_CHAIN_APPROX_NONE,
    Point(0, 0)); // all pixels of each contours    

// Draw black contours on a white image
Mat result(threshold_output.size(),CV_8U,Scalar(255));
drawContours(result,contours,
    -1, // draw all contours
    Scalar(0), // in black
    2); // with a thickness of 2

//Bounding Box
//vector<Point> points;
//Mat_<uchar>::iterator it = result.begin<uchar>(); Mat_<uchar>::iterator end = result.end<uchar>(); for (; it != end; ++it) { if (*it) points.push_back(it.pos()); }

//RotatedRect box = minAreaRect(Mat(points));
RotatedRect box = minAreaRect(contours[0]);

Point2f vertices[4];
box.points(vertices);
 Mat ViewMat;
 cvtColor(image_gray,ViewMat,CV_GRAY2BGR);
for (int i = 0; i < 4; ++i)
    {
        line(ViewMat, vertices[i], vertices[(i + 1) % 4], cv::Scalar(0, 255, 0), 1, CV_AA);
    }



Rect your_roi;
your_roi.x = box.center.x - (box.size.width / 2);
your_roi.y = box.center.y - (box.size.height / 2);
your_roi.width = box.size.width;
your_roi.height = box.size.height;   
rectangle(ViewMat,your_roi,bh_red);

//Create Window
Rect roi=  boundingRect(contours[0]);
rectangle(ViewMat,roi,bh_blue);

rectangle(ViewMat,box.boundingRect(),bh_yellow);

bhDrawColorLabel(ViewMat,"your method",bh_red,0);
bhDrawColorLabel(ViewMat,"your method2",bh_green,1);
bhDrawColorLabel(ViewMat,"boundingRect",bh_blue,2);
bhDrawColorLabel(ViewMat,"RotatedRect.boundingRect",bh_yellow,3);

char* DisplayWindow = "Source";
namedWindow(DisplayWindow, CV_WINDOW_AUTOSIZE);
imshow(DisplayWindow, ViewMat);



waitKey(0);
return 1;
}

Opencv-bounding-box-2.png

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