Opencv2示例程序不工作

我正试图让opencv2代码在我的Ubuntu 12.04上工作。看来库安装正确了。

这里是示例代码，我试图得到的工作

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
using namespace cv;
int main(int argc, char ** argv)
{
    // Read image and write to matrix - here converted to grayimage by "0"
    Mat myimage = imread ( argv[1], 0 );
    // Show it in a window
    imshow ( "MyWindowTitle", myimage);
    // Wait for a keypress ( for x [ms], 0 means infinity )
    waitKey(0);
}

我将这段代码编译为:

g++ -o sample `pkg-config --cflags --libs opencv` sample.cpp

然而，我得到以下编译错误:

/tmp/cccMPtyu.o: In function `main':
imshow.cpp:(.text+0x59): undefined reference to `cv::imread(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int)'
imshow.cpp:(.text+0x92): undefined reference to `cv::_InputArray::_InputArray(cv::Mat const&)'
imshow.cpp:(.text+0xc9): undefined reference to `cv::imshow(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, cv::_InputArray const&)'
imshow.cpp:(.text+0xeb): undefined reference to `cv::waitKey(int)'
/tmp/cccMPtyu.o: In function `cv::Mat::~Mat()':
imshow.cpp:(.text._ZN2cv3MatD2Ev[_ZN2cv3MatD5Ev]+0x2b): undefined reference to `cv::fastFree(void*)'
/tmp/cccMPtyu.o: In function `cv::Mat::release()':
imshow.cpp:(.text._ZN2cv3Mat7releaseEv[cv::Mat::release()]+0x3b): undefined reference to `cv::Mat::deallocate()'
collect2: ld returned 1 exit status

可能的原因是什么?我该如何改正呢?

也可以有人建议一个很好的教程，特别是openv2。我以前使用opencv1编程，但似乎有很多变化。