I know I can't be the first person to want this, but after a day and a half of searching I can't find anything to fit the bill and I find that odd.
Workflow: Shoot photo on android... make it Black white (not gray but really 1 bit)... save it as a PNG, preferably true 1-bit or at least indexed color in order to make a small file size and keep the data.
Doing the convert to gray to b&w wasn't a problem. I have that done. But its still a 900kb file when it could be 50k. I'm sure that's because its still being saved as a full-color image. I'm thinking that if I turn that into indexed color of only 2 colors then it should be at least 10 times smaller.
I was hoping to avoid adding huge libraries that are vastly overkill for this one need. Researching I find reference to Android libraries such a pngj that have this small scope of need but they date back to 2013/2014 - Making me think something else has risen up to take their place but I can't for the life of me find something to handle this need in today's era: Preferably something Xamarin friendly.