Someone helped me get this code for taking a picture using xamarin forms labs camera:
picker = DependencyService.Get ();
An update from the Xamarin Media Plugin allows you to resize the image https://github.com/jamesmontemagno/MediaPlugin ... barring that, and you need a more generic resize option (say the image comes from a web call, and not the device, then have a look at: https://github.com/InquisitorJax/Wibci.Xamarin.Images