Update image tinting to use UIGraphicsImageRenderer where possible

[ZevEisenberg]

UIGraphicsImageRenderer supports wide color, and UIGraphicsBeginImageContext does not. We should use the former on OSes that support it.

Questions:

• does macOS have an equivalent image renderer?
• We currently have a convoluted image tinting function with a lot of conditional compilation. Can we imrprove this situation? Will we need to, in order to add a third or possibly fourth permutation of how we render?

[shaps80]

Hi,

I've actually been using your library for a while now. Great work btw.

I came across this Issue and thought you might be interested in my port:
https://github.com/shaps80/GraphicsRenderer

It's backward compatible & supports macOS. I don't think I've updated it to support wide colour, but that shouldn't be a huge task. Its also been designed to map the APIs directly, I was originally using it and then just dropping the prefix once I no longer needed it.

Anyway, maybe it's useful as a starting point.

[ZevEisenberg]

@shaps80 thanks for sharing! I'll check it out if/when I get around to implementing this change.