image_transport_plugins compressed_image_transport: image decompression as a stand-alone function.

This relates to #49.

Basically a refactoring: It exposes image decompression as a stand-alone function in a separate lib. Additionally, it refactors the compressed subscriber to use that function.

@dgossow Could you please review this pull request?

Feb 27 '20 13:02 airballking

I just saw that the Travis build for Kinetic failed because I used a C++11 feature for generating meaningful error messages. I will fix that.

Mar 10 '20 13:03 airballking

Just pushed a commit that should fix the compilation issues for Kinetic, i.e. no longer using C++11 feature std::to_string. Let's see what Travis says.

Mar 12 '20 12:03 airballking

@dgossow The build now passes on Travis.

I also checked the refactoring on my laptop by bringing up a usb_cam node as a source, starting a rqt_image_view node as a sink, and then played with various compression settings while viewing the compressed image. Worked fine.

@dgossow Could you please have a look at this pull request?

Mar 12 '20 12:03 airballking