golang gocv error when go run ./cmd/version/main.go - opencv

Question

I'm pretty new in Golang and i have some problems to install gocv.
I don't know weather it is impotent to know, but
I use Manjaro Linux on version 5.19.3, the current go- version is 1.14.2 and last but not least gccgo on version 10.1.0 (amd64).
I installed gocv as described on https://gocv.io/getting-started/linux/
go get -u -d gocv.io/x/gocv
cd $GOPATH/pkg/mod/gocv.io/
make install
If it works correctly, following message should be desplayed:
gocv version: 0.24.0
opencv lib version: 4.4.0
# gocv.io/x/gocv
In file included from features2d.cpp:1:
features2d.h:22:21: error: 'SIFT' is not a member of 'cv'
22 | typedef cv::Ptr<cv::SIFT>* SIFT;
| ^~~~
features2d.h:22:21: error: 'SIFT' is not a member of 'cv'
features2d.h:22:25: error: template argument 1 is invalid
22 | typedef cv::Ptr<cv::SIFT>* SIFT;
| ^
features2d.cpp: In function 'int* SIFT_Create()':
features2d.cpp:434:28: error: 'SIFT' is not a member of 'cv'; did you mean 'SIFT'?
434 | return new cv::Ptr<cv::SIFT>(cv::SIFT::create());
| ^~~~
In file included from features2d.cpp:1:
features2d.h:22:28: note: 'SIFT' declared here
22 | typedef cv::Ptr<cv::SIFT>* SIFT;
| ^~~~
features2d.cpp:434:28: error: 'SIFT' is not a member of 'cv'; did you mean 'SIFT'?
434 | return new cv::Ptr<cv::SIFT>(cv::SIFT::create());
| ^~~~
In file included from features2d.cpp:1:
features2d.h:22:28: note: 'SIFT' declared here
22 | typedef cv::Ptr<cv::SIFT>* SIFT;
| ^~~~
features2d.cpp:434:32: error: template argument 1 is invalid
434 | return new cv::Ptr<cv::SIFT>(cv::SIFT::create());
| ^
features2d.cpp:434:38: error: 'cv::SIFT' has not been declared
434 | return new cv::Ptr<cv::SIFT>(cv::SIFT::create());
| ^~~~
features2d.cpp: In function 'KeyPoints SIFT_Detect(SIFT, Mat)':
features2d.cpp:443:9: error: base operand of '->' is not a pointer
443 | (*d)->detect(*src, detected);
| ^~
features2d.cpp: In function 'KeyPoints SIFT_DetectAndCompute(SIFT, Mat, Mat, Mat)':
features2d.cpp:460:9: error: base operand of '->' is not a pointer
460 | (*d)->detectAndCompute(*src, *mask, detected, *desc);
| ^~
Fehler: Prozess beendet mit Rückgabewert 2.
I tried to find a solution on in the internet, but I don't even understand the problem.
I hope someone can help me.
best regards
Felix

Answer 1

SIFT (Scale-Invariant Feature Transform) algorithm is a patented algorithm that requires user to import a non-free header file if you need to use it as below :
#include <opencv2/nonfree/nonfree.hpp>
However, the patent is already expired as of now. (OpenCV 4.4.0) So this package is moved to main repository of opencv (check release highlightes https://opencv.org/opencv-4-4-0/)
As a result,the gocv repository which using SIFT has been updated to get this algorithm from the opencv main repository as below, (in gocv v0.24.0 change log: https://github.com/hybridgroup/gocv/commit/04b71cbb6d82e8c396ccbbf0d65b446a80a0e8fa)
typedef cv::Ptr<cv::SIFT>* SIFT;
This is the line of code updated which causes you failed to build.(You will only get this error if you are not using opencv 4.4.0, you may check the MakeFile that you are using)
To solve this problem, you may try get/update the gocv repository again now as they have updated all MakeFile to use opencv 4.4.0 already. Or you may just manually update your MakeFile to change the opencv version to 4.4.0