iteration times on Windows seem unbearable about gocv HOT 7 CLOSED

Actually, I dug into things a bit more and a great deal of this pain was me being unfamiliar with the proper care and feeding of cgo modules. The instructions at https://gocv.io/getting-started/windows/ download gocv using go get, then install the OpenCV native libraries, then tell you to go off and write code. While this works, it means that even if you're just a consumer of the gocv library and not hacking on it at all, you'll still be compiling it from scratch every time you compile your own program.

I now recommend the setup instructions be amended to reflect this.

As written, the instructions are perfect for someone who wants to contribute to gocv development.

For someone who wants to consume gocv as a library, there should be a section after the mingw32-make install step, and before the "how to build/run code" step, that recommends running go install gocv.io/x/gocv. This will pre-build the gocv library into a gocv.a file that's stored under the {GOPATH}/pkg folder. Then when you write and run an example program that consumes the gocv package, go build will merely link with that library, and you will get the < 1s build/link times that you would expect from a typical toy program.

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Hi @directive-cary I would say that the performance of C++ compilation/linking in general of any large project is not great, as I am sure you discovered when installing OpenCV itself.

Also, Windows in general is much slower when compiling C++ using open source toolchains. This is not specific to GoCV itself, but part of needing to compile/link against a large C++ codebase using CGo.

You might want to experiment with precompiled headers, which I have not had time to explore. They are turned off in the Windows build atm due to some incompatibilities in the build I did not dig too far into.

Hope that helps!

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That is a very good idea @directive-cary any interest in committing a PR with that info added to the README?

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After thinking about a couple different wordings, I decided that being succinct in the readme worked better than a paragraph giving the full explanation of what happens and why to do it. I hope this matches what you expected. :)

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Thanks for the PR @directive-cary I will close this issue once the next GoCV release is out.

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This documentation was released as part of v0.8.0 so now closing. Thanks again!

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I encountered the same in Linux. Running go install gocv.io/x/gocv like @directive-cary mentioned fixed the issue.

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