gmic 2.9.7.x: OpenCV support no longer enabled by default

[mascguy (Christopher Nielsen)]

It looks like gmic changed the default build options starting with 2.9.7, such that OpenCV is no longer enabled by default.

The portfile now needs to include the following configure option:

-DENABLE_OPENCV=ON

I'll take care of fixing this, since I'm updating opencv4 to 4.5.2 anyway. That update is covered by the following pull request:

​https://github.com/macports/macports-ports/pull/10768

[Schamschula (Marius Schamschula)]

Indeed. That's an upstream change. See: ​https://discuss.pixls.us/t/on-the-road-to-3-0/17226 ( In the From 2.9.6 to 2.9.7 section)

opencv support should probably be included as a variant.

[mascguy (Christopher Nielsen)]

While it sounds like OpenCV isn't used for much, I'd hate to potentially affect any of our users by switching to a variant. Up to you though.

[mascguy (Christopher Nielsen)]

Pull request created:

​https://github.com/macports/macports-ports/pull/10771

We can go with the variant approach if you want, but let's discuss via the PR.

[Schamschula (Marius Schamschula)]

Understood. However, I'm following upstream.

No need for a PR, I've already updated the Portfile locally and will push it to GitHub shortly.

[mascguy (Christopher Nielsen)]

Marius, can you include my fix, to eliminate the need to patch the opencv library path?

[mascguy (Christopher Nielsen)]

Specifically the following:

    # insert path to opencv4 libraries, as cmake fails to do so
    configure.ldflags-append    -L${prefix}/lib/opencv4

[mascguy (Christopher Nielsen)]

Plus enabling parallel builds, which I also included in my PR.

[Schamschula (Marius Schamschula)]

I'm test building with both of your changes.

[Schamschula (Marius Schamschula)]

In 70c8c88ec321823c87c1b8fa17219890210e7e89/macports-ports (master):

gmic: add opencv variant

enable parallel builds
use configure.ldflags-append rather than patch for opencv lib path
Closes: #62738
See: ​https://github.com/macports/macports-ports/pull/10771