OpenCV bottle/liquid measurement - c++

Question

Ok, I need to compute the distance between the cap (top of the bottle) and the liquid. I am trying to get the color pixel by pixel from the top down to the liquid. Any ideas how can I do that measure? (I am not sure how to use dilate properly)
#include <opencv/cvaux.h>
#include <opencv/highgui.h>
#include <opencv/cxcore.h>
#include <stdio.h>
#include <stdlib.h>
using namespace cv;
using namespace std;
Mat src = imread("cocaCorte.jpg");
Mat srcTampa, srcLiquido, pixelColor;
Point3_<uchar>* p;
int posicaoX,posicaoY;
void find_moments( Mat grey );
int main(int argc, char* argv[])
{
///Criacao das janelas
cvNamedWindow( "Original", CV_WINDOW_AUTOSIZE);
cvNamedWindow( "Tampa Processada", CV_WINDOW_AUTOSIZE);
cvNamedWindow( "Liquido Processado", CV_WINDOW_AUTOSIZE);
cvNamedWindow( "Bitwise OR", CV_WINDOW_AUTOSIZE);
///Processamento do liquido
inRange( src, Scalar( 0, 0, 0), Scalar( 60, 60, 60), srcLiquido);
GaussianBlur( srcLiquido, srcLiquido, Size( 7, 7), 5, 5);
threshold( srcLiquido, srcLiquido, 100, 255, CV_THRESH_BINARY);
dilate( srcLiquido, srcLiquido, Mat(), Point(-1, -1), 2, 1, 1);
dilate( srcLiquido, srcLiquido, Mat(), Point(-1, -1), 2, 1, 1);
dilate( srcLiquido, srcLiquido, Mat(), Point(-1, -1), 2, 1, 1);
dilate( srcLiquido, srcLiquido, Mat(), Point(-1, -1), 2, 1, 1);
dilate(srcLiquido, srcLiquido, Mat(), Point(-1, -1), 2, 1, 1);
dilate(srcLiquido, srcLiquido, Mat(), Point(-1, -1), 2, 1, 1);
///Processamento da tampa
inRange( src, Scalar( 25, 20, 138), Scalar( 90, 115, 205), srcTampa);
GaussianBlur( srcTampa, srcTampa, Size( 7, 7), 5, 5);
threshold( srcTampa, srcTampa, 100, 255, CV_THRESH_BINARY);
find_moments( srcTampa);
///Juntar as duas imagens
bitwise_or( srcTampa, srcLiquido, pixelColor);
///Calculos
///Reach the white part represent by the liquid starting fromthe top
while(true){
p = pixelColor.ptr<Point3_<uchar> >( posicaoY, posicaoX);
if((p->z=0)&&(p->y=0)&&(p->x=0)){
//that means the liquid was found
break;
}
posicaoY++;
}
cout<<"FOUND"<<endl; //Print the result...
///Mostrar imagens
imshow("Tampa Processada", srcTampa);
imshow("Liquido Processado", srcLiquido);
imshow("Bitwise OR", pixelColor);
waitKey();
destroyAllWindows();
return 0;
}
void find_moments( Mat gray )
{
Mat canny_output;
vector<vector<Point> > contours;
vector<Vec4i> hierarchy;
/// Detect edges using canny
Canny( gray, canny_output, 50, 150, 3 );
/// Find contours
findContours( canny_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );
/// Get the moments
vector<Moments> mu(contours.size() );
for( int i = 0; i < contours.size(); i++ )
{
mu[i] = moments( contours[i], false );
}
/// Get the mass centers:
vector<Point2f> mc( contours.size() );
for( int i = 0; i < contours.size(); i++ )
{
mc[i] = Point2f( mu[i].m10/mu[i].m00 , mu[i].m01/mu[i].m00 );
}
posicaoX = mc[0].x;
posicaoY = mc[0].y;
/// Draw contours
for( int i = 0; i< contours.size(); i++ )
{
Scalar color = Scalar( 255, 0, 0);
drawContours( src, contours, i, color, 2, 8, hierarchy, 0, Point() );
circle(src, mc[i], 2, color, -1, 1, 0 );
}
/// Show in a window
namedWindow( "Contours", CV_WINDOW_AUTOSIZE );
imshow( "Contours", src );
}