Linking error of openCV 2.3.1 findContours function - c++

Question

when i am trying to run the finding squares code with Visual Studio 2008, it gives the following error.
1>ANPR.obj : error LNK2001: unresolved external symbol "public: virtual class cv::GlBuffer __thiscall cv::_InputArray::getGlBuffer(void)const " (?getGlBuffer#_InputArray#cv##UBE?AVGlBuffer#2#XZ)
1>ANPR.obj : error LNK2001: unresolved external symbol "public: virtual class cv::GlTexture __thiscall cv::_InputArray::getGlTexture(void)const " (?getGlTexture#_InputArray#cv##UBE?AVGlTexture#2#XZ)
1>ANPR.obj : error LNK2001: unresolved external symbol "public: virtual class cv::gpu::GpuMat __thiscall cv::_InputArray::getGpuMat(void)const " (?getGpuMat#_InputArray#cv##UBE?AVGpuMat#gpu#2#XZ)
Code :
#include <cv.h>
#include <highgui.h>
using namespace cv;
double angle( cv::Point pt1, cv::Point pt2, cv::Point pt0 )
{
double dx1 = pt1.x - pt0.x;
double dy1 = pt1.y - pt0.y;
double dx2 = pt2.x - pt0.x;
double dy2 = pt2.y - pt0.y;
return (dx1*dx2 + dy1*dy2)/sqrt((dx1*dx1 + dy1*dy1)*(dx2*dx2 + dy2*dy2) + 1e-10);
}
void find_squares(Mat& image, vector<vector<Point> >& squares)
{
// blur will enhance edge detection
Mat blurred(image);
medianBlur(image, blurred, 9);
Mat gray0(blurred.size(), CV_8U), gray;
vector<vector<Point> > contours;
// find squares in every color plane of the image
for (int c = 0; c < 3; c++)
{
int ch[] = {c, 0};
mixChannels(&blurred, 1, &gray0, 1, ch, 1);
// try several threshold levels
const int threshold_level = 2;
for (int l = 0; l < threshold_level; l++)
{
// Use Canny instead of zero threshold level!
// Canny helps to catch squares with gradient shading
if (l == 0)
{
Canny(gray0, gray, 10, 20, 3); //
// Dilate helps to remove potential holes between edge segments
dilate(gray, gray, Mat(), Point(-1,-1));
}
else
{
gray = gray0 >= (l+1) * 255 / threshold_level;
}
// Find contours and store them in a list
findContours(gray, contours, CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE);
// Test contours
vector<Point> approx;
for (size_t i = 0; i < contours.size(); i++)
{
// approximate contour with accuracy proportional
// to the contour perimeter
approxPolyDP(Mat(contours[i]), approx, arcLength(Mat(contours[i]), true)*0.02, true);
// Note: absolute value of an area is used because
// area may be positive or negative - in accordance with the
// contour orientation
if (approx.size() == 4 &&
fabs(contourArea(Mat(approx))) > 1000 &&
isContourConvex(Mat(approx)))
{
double maxCosine = 0;
for (int j = 2; j < 5; j++)
{
double cosine = fabs(angle(approx[j%4], approx[j-2], approx[j-1]));
maxCosine = MAX(maxCosine, cosine);
}
if (maxCosine < 0.3)
squares.push_back(approx);
}
}
}
}
}
int main()
{
Mat img = imread("peppers.jpg");
cvtColor(img, img, CV_RGB2GRAY);
vector<vector<Point> > squares;
find_squares(img, squares);
std::cout << "squares size: " << squares.size() << std::endl;
getchar();
return 0;
}
Can somebody help me to solve this? I tried openCV 2.4.2.It gave the same linking error.
thankz

Answer 1

These errors are related to the linking process, and the symbols you mentioned belong to the opencv_core library.
Make sure you've added this library as a dependency of your project. Go to Configuration Properties > Linker > Input and add: opencv_core242.lib
For more instructions on how to configure Visual Studio & OpenCV, check this thread.