Use OpenCV 3.2 on Buster

[sloretz]

This should fix the binary job for image_publisher on Debian Buster. It uses OpenCV 3 if OpenCV 4 is not available.

http://build.ros.org/view/Nbin_db_dB64/job/Nbin_db_dB64__image_publisher__debian_buster_amd64__binary/4/

@SteveMacenski @JWhitleyWork assuming the change looks ok to you, would you be willing to make a new Noetic release with it today?

[SteveMacenski]

@sloretz I'm surprised if there's not more code changes that need to be made for OpenCV3. I thought some of the enums changed as part of the OpenCV4 transition. Can you confirm local evidence that this solves your problem in OpenCV3 on Buster in the current state of this PR without any code modifications?

[sloretz]

Can you confirm local evidence that this solves your problem in OpenCV3 on Buster in the current state of this PR without any code modifications?

I built and ran tests locally in both a Buster and Focal container. I was surprised by it too. As far as I can tell the only code changes to image_publisher for OpenCV 4 were in this file in #530

https://github.com/ros-perception/image_pipeline/pull/530/files#diff-cf9b4f0fb39104a4d4fdac9e6c63846a

Maybe those changes were related to droping OpenCV 2 support? They look compatible with OpenCV 3 and 4.

1. CV_PROP_POS_FRAMES -> cv::CV_PROP_POS_FRAMES

It looks like CV_PROP_POS_FRAMES was already in the cv namespace in OpenCV 3.2
https://docs.opencv.org/3.2.0/d4/d15/group__videoio__flags__base.html#ggaeb8dd9c89c10a5c63c139bf7c4f5704da6223452891755166a4fd5173ea257068

2. CV_LOAD_IMAGE_COLOR -> cv::IMREAD_COLOR

It looks like cv::IMREAD_COLOR already existed in OpenCV 3.2

https://docs.opencv.org/3.2.0/d4/da8/group__imgcodecs.html#gga61d9b0126a3e57d9277ac48327799c80af660544735200cbe942eea09232eb822

[SteveMacenski]

🤷 I'll go with it.

[SteveMacenski]

You should see a PR on rosdistro now with your name on it