Like others mentioned, you need to make sure you’re linking to the OpenCV libs correctly.
Check that your Project -> Properties -> VC++ Directories -> Library Directories, includes the path where the OpenCV libraries are, the default would be ‘C:\opencv\build\x86\vc11\lib’ (on a 32-bit machine running VS2012, it will vary on other setups).
Next, check that the following libraries are included in your Project -> Properties -> Linker -> Input -> Additional Dependencies :
opencv_core246d.lib
opencv_imgproc246d.lib
opencv_highgui246d.lib
opencv_ml246d.lib
opencv_video246d.lib
opencv_features2d246d.lib
opencv_calib3d246d.lib
opencv_objdetect246d.lib
opencv_contrib246d.lib
opencv_legacy246d.lib
opencv_flann246d.lib
If the above are correct, you shouldn’t get any more OpenCV link errors.