【opencv练习36 - 图像moment】

/*******************************************************************
测试程序【目标面积】
时间：2016年9月3日
********************************************************************/

Mat src; Mat src_gray;
int thresh = 100;
int max_thresh = 255;
RNG rng(12345);

void thresh_callback(int, void* );

int main(void)
{
src = imread("moments.jpg", 1 );
cvtColor( src, src_gray, COLOR_BGR2GRAY );
blur( src_gray, src_gray, Size(3,3) );

const char* source_window = "Source";
namedWindow( source_window, WINDOW_AUTOSIZE );
imshow( source_window, src );

createTrackbar( " Canny thresh:", "Source", &thresh, max_thresh, thresh_callback );
thresh_callback( 0, 0 );

waitKey(0);
return(0);
}

void thresh_callback(int, void* )
{
Mat canny_output;
vector<vector<Point> > contours;
vector<Vec4i> hierarchy;

// 【1、Canny边缘检测 + 查找轮廓 src_gray——>canny_output——>contours】
Canny( src_gray, canny_output, thresh, thresh*2, 3 );
findContours( canny_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );

// 【2、获取moments（moments向量）    contours——> moments(mu) ——>Point2f(nc)】
vector<Moments> mu(contours.size() );
for( size_t i = 0; i < contours.size(); i++ )
{
mu[i] = moments( contours[i], false );
}

//【Get重心】
vector<Point2f> mc( contours.size() );
for( size_t i = 0; i < contours.size(); i++ )
{
mc[i] = Point2f( static_cast<float>(mu[i].m10/mu[i].m00) , static_cast<float>(mu[i].m01/mu[i].m00) );
}

//【3、绘制轮廓】
Mat drawing = Mat::zeros( canny_output.size(), CV_8UC3 );
for( size_t i = 0; i< contours.size(); i++ )
{
Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
drawContours( drawing, contours, (int)i, color, 2, 8, hierarchy, 0, Point() );
circle( drawing, mc[i], 4, color, -1, 8, 0 );
}

// Show
namedWindow( "Contours", WINDOW_AUTOSIZE );
imshow( "Contours", drawing );

//【计算面积，和Opencv的面积函数比较】
printf("Info: Area and Contour Length \n");
for( size_t i = 0; i< contours.size(); i++ )
{
printf(" * Contour[%d] - Area (M_00) = %.2f \n", (int)i,mu[i].m00);//m00 面积
printf(" * Contour[%d] - Area OpenCV: %.2f - Length: %.2f \n", (int)i, contourArea(contours[i]),arcLength( contours[i], true ) );   //长度

Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
drawContours( drawing, contours, (int)i, color, 2, 8, hierarchy, 0, Point() );       //绘制轮廓
circle( drawing, mc[i], 4, color, -1, 8, 0 );                                        //绘制圆心
}
}