Add Actual Camera Resolution Property

[direkrain]

I'm trying to implement a scan window where the app must ignore QR codes not inside it.
I was able to map them in the screen coordinates using the pre-defined resolution values.
The problem is, when you specify the camera resolution, it will use the nearest supported resolution which makes the app behavior very unpredictable.

The workaround I did is to load the image returned just to get the width and the height. It is close, but not perfect. Plus, it added more unnecessary processes and memory allocation.