[Buildroot] [PATCH 1/1] package/vlc: fix build with opencv3

[Thomas Petazzoni <thomas.petazzoni@bootlin.com>]

Hello Fabrice,

On Fri, 28 Feb 2020 14:38:09 +0100
Fabrice Fontaine <fontaine.fabrice@gmail.com> wrote:

> Fixes:
>  - http://autobuild.buildroot.org/results/210424bd33f660aa0757f62a558e1e03faf0f371
> 
> Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
> ---
>  ...lter-opencv_example.cpp-fix-build-wi.patch | 38 +++++++++++++++++++
>  1 file changed, 38 insertions(+)
>  create mode 100644 package/vlc/0010-modules-video_filter-opencv_example.cpp-fix-build-wi.patch
> 
> diff --git a/package/vlc/0010-modules-video_filter-opencv_example.cpp-fix-build-wi.patch b/package/vlc/0010-modules-video_filter-opencv_example.cpp-fix-build-wi.patch
> new file mode 100644
> index 0000000000..04c9958298
> --- /dev/null
> +++ b/package/vlc/0010-modules-video_filter-opencv_example.cpp-fix-build-wi.patch
> @@ -0,0 +1,38 @@
> +From 67244e60fc1d8c7a9350bac30611f56c398761e5 Mon Sep 17 00:00:00 2001
> +From: Fabrice Fontaine <fontaine.fabrice@gmail.com>
> +Date: Fri, 28 Feb 2020 14:29:47 +0100
> +Subject: [PATCH] modules/video_filter/opencv_example.cpp: fix build with
> + opencv 3.4.9
> +
> +Convert CV_RGB to cvScalar to avoid the following build failure with
> +opencv 3.4.9:
> +
> +In file included from /home/naourr/work/instance-2/output-1/host/x86_64-buildroot-linux-uclibc/sysroot/usr/include/opencv2/imgproc/imgproc.hpp:48,
> +                 from video_filter/opencv_example.cpp:46:
> +video_filter/opencv_example.cpp: In function 'picture_t* Filter(filter_t*, picture_t*)':
> +video_filter/opencv_example.cpp:200:46: error: could not convert 'cv::Scalar_<double>((double)0, (double)0, (double)0, (double)0)' from 'cv::Scalar' {aka 'cv::Scalar_<double>'} to 'CvScalar'
> +             cvRectangle( p_img[0], pt1, pt2, CV_RGB(0,0,0), 3, 8, 0 );

Thanks for looking into this. I must say I don't feel very confident
about the fix. Have you been able to trace which change in OpenCV
caused this build issue ?

Also, is the fix still compatible with OpenCV 2.x ? Indeed, VLC
requires OpenCV > 2.0, so I guess it can still work with some 2.x
OpenCV version.

Have you considered talking with the OpenCV community to see what is
the proper fix ?

Thanks!

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com