Minor but very important convenience feature, especially useful when
dealing with command-line apps. This now works:
magnum-imageconverter a.png a.jpg -c jpegQuality=0.75
The AnyImageConverter gets the jpegQuality option and then
automatically propagates it to the concrete plugin (which is either
JpegImageConverter or StbImageConverter), possibly warning in case the
target plugin doesn't recognize given option (i.e., doesn't list it in
its default configuration). Previously the user had to always specify a
concrete converter implementation using -C, which was rather annoying
and nonintuitive.
It should be input first, output second, like with all other APIs. I
remember I was trying something else here, but that didn't really make
sense in the end. Also took that opportunity to get rid of one
std::string.
The original signature is a deprecated alias to the new one and will be
removed in a future release.
It doesn't really work for tests that depend on more than one plugin
(because there i would need to handle all combinations, somehow), but it
does the job when the end user has such use case.