Maximilian Matthe

Within the file `include/rgbvalue.hxx`, some template class names are `DIFFERENCE`. This collides with a strange define within the file [`winuser.h` within the mingw-w64 package](https://sourceforge.net/p/mingw-w64/mingw-w64/ci/master/tree/mingw-w64-headers/include/winuser.h#l135).

thanks for the great project! I use it to make still images of my gas meter, to process later on. Unfortunately, it occurs randomly (like 5% of the taken photos)...

Instead of jumping from one face size to another, do a smooth filtering between the current and target state.

Reduce computational load by doing the face detection on a smaller image. Hence,, achieve higher frame rate.