How to use opencv cuda module log function - opencv

Question

I'm trying to work with Opencv CUDA module, specially refer to cv::cuda::log function.
First, I'll give to details Opencv compilation.
I compiled Opencv with WITH_CUDA flag on, took the libs and dlls from the compilation, however I copied the headers files from the downloaded opencv folder, since the compilation folder does't include headers by default.
I wonder, whether is this the right thing to do ?
Second, I tried to use the cv::cuda:: function.
I include the cuda.hpp header
#include "opencv2/core/cuda.hpp"
cv::cuda::GpuMat source, dest;
GpuMat compiles great for me, However I don't know which file should I include in order to work with the log function. when I write the following line
cv::cuda::log(source, dest);
I kept on getting the error message:
error: C2039: log in not a member of cv::cuda
Windows 7, Visual studio 2013, Opencv 3.0.0, platform: 64 bit, CUDA toolkit 6.5
Third, I'd like to know about Opencv CUDA implementation, does it utilize npp functionality? Opencv vs npp, which one is better to use ?
I could easly write my code using npp, however I'd like to know the opencv CUDA module.
Thanks

Answer 1

After couple days of searching, I'd like to share my knowledge
First thing I was doing wrong, was taking the headers from Opencv compilation, the right thing to do is taking the header from all the Opencv modules (each module individually).
Second, After Opencv compilation with CUDA flag everything worked great.
Third, Several opencv CUDA functions does utilize NPP
Forth, Use github

Answer 2

This code should work for OpenCV 3.1:
#include <opencv2/opencv.hpp>
#include <opencv2/cudaarithm.hpp>
int main()
{
cv::Mat img = cv::imread("img.jpg", cv::IMREAD_GRAYSCALE);
cv::Mat img_32f;
img.convertTo(img_32f, CV_32F);
//To avoid log(0) that is undefined
img_32f += 1.0f;
cv::cuda::GpuMat gpuImg, gpuImgLog;
gpuImg.upload(img_32f);
cv::cuda::log(gpuImg, gpuImgLog);
cv::Mat imgLog, imgLog_32f;
gpuImgLog.download(imgLog_32f);
double min, max;
cv::minMaxLoc(imgLog_32f, &min, &max);
imgLog_32f.convertTo(imgLog, CV_8U, 255.0/(max-min), -255.0*min/(max-min));
cv::imshow("img", img);
cv::imshow("imgLog", imgLog);
cv::waitKey(0);
return 0;
}