opencv::cuda GpuMat CV_8UC1 到 CV_32FC1 转换黑色图像

Question

I am converting opencv-python operations to c++ opencv::cuda for better performance but I have a problem about CV_8UC1 to CV_32FC1 convertion.

Python Code I want to convert:

img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
img_float = np.float32(img_gray)
img_log = cv2.log(img_float)
print(img_log[100,100]) //Prints 5.325 floating value
cv2.imwrite("log_py.jpg", img_log) // shows log transformed image

C++ Code :

cv::Mat src_host = cv::imread("crack2.jpg");
cv::Mat dst;
cv::cuda::GpuMat dst, src, log, gray_gpu;
src.upload(src_host);
cv::cuda::cvtColor(src, gray_gpu, cv::COLOR_BGR2GRAY);
gray_gpu.convertTo(gray_gpu, CV_32FC1);
cv::cuda::log(gray_gpu, log);
log.download(dst);
std::cout << "float : " << (float)(dst.at<float>(100,100)) << std::endl; //Prints 0 integer value
std::cout << "int : " << (int)(dst.at<uchar>(100,100)) << std::endl; //prints 128 integer value
cv::imwrite("log_cpp.jpg", dst); //shows black image

If I don't convert to CV_32FC1 it applies log transformation but images won't be same. I need to apply this log operation to floating value. What should I do? , ( @zindarod )

Answer 1

In-place operations do not seem to be working for opencv::cuda::GpuMat::convertTo function.

See these posts:

https://github.com/opencv/opencv/issues/13092

https://answers.opencv.org/question/97672/converting-gpumat-32fc1-8uc1/?answer=97690#post-id-97690

---

As a workaround, you can declare a new temporary variable and perform the operation on that variable:

cv::cuda::GpuMat gray_gpu_temp;
cv::cuda::cvtColor(src, gray_gpu_temp, cv::COLOR_BGR2GRAY);
gray_gpu_temp.convertTo(gray_gpu, CV_32FC1);