Make slideextract self-contained and cross-platform

[aminya]

• Now the library works on all platforms. Tested it on Windows, and it works! 🎉
• Added Cmake and Conan for installation and building of the packages.
• Replaced Linux specific header file (unistd) with the awesome cargs library which is cross-platform and nicer to work with.
• Updated the readme
• Fixed the generation of empty images
• Support selecting the region from all directions in GUI

[aminya]

@szanni Check this out!

I am also interested to add continuous integration for providing binaries to make it easier for the average user to use this awesome tool.

[szanni]

Thanks for the effort and the hidden bug report but I hope this does not come off as too hash - pretty much the whole patch set won't fly...

• Thanks for reporting that the comparison region could only be selected from top-left to bottom right. This was a bug. But this can and should be solved by simple math and not 30 lines of added temp variables, if's, and convoluted logic. See 35cde374b4f1bc1ecd0be2597dc8e39a8390bf1b
• There is no way I will add Cmake. If you had seen the CHANGELOG (yeah who reads those right?) you would have seen that I just removed the monstrosity called autotools. No way will I add back something similar.
• The same goes for conan. Never heard of it. It does not even have a Wikipedia entry and seems to be some type of corporate backed advertising thingy. Apparently QT6 added some integration?! But a no from my side until the platform looks mature.
• <cargs.h> looks nice, the function naming IMO is crap. Not your fault but again nope. If it was a single header file library - then maybe - but not in this form.
• And I dislike making anything even more manual.

Regarding windows: does anyone use windows command line tools for stuff like this these days? I though command line inclined people were using WSL2 these days anyways? Regarding mac: mac has macports and homebrew if anyone feels inclined to add support.

Regarding CI: the free services are changing all the time, I don't feel like constantly fixing this. A manual test suite would be amazing though. Automated CI IMO is warranted for bigger projects with many moving parts but for a small tool like this most likely more work than work saving.

And finally regarding binaries: there is no way I will distribute anything the like. If you feel so inclined - be my guest - I will not. This is due to opencv including tons of patented tech - video codecs and the like. It is beautiful we have open source projects like VLC media player, they are however backed by the VideoLan organization and a lot of people would jump in to fight a legal battle. I have no such backing and am not willing to take the risk.

[aminya]

NP