Missing implementation for From<Rgb555> and From<Rgb565> #238
Description
Hi,
I'm trying to render a BMP image to a 7-color waveshare display.
The embedded-graphics has support for BMP images using the tinybmp crate, and it allows to specify a color space (eg Bmp::<OctColor>::from_slice(...)) but OctColor needs to implement From<Rgb555> and From<Rgb565>.
Right now this crate implements only From<embedded_graphics_core::pixelcolor::Rgb888>.
The implementation could be similar to the Rgb888 one, that tries to find the closest colors.
I'd make a PR but sadly I'm not familiar with graphics at all.
Just for testing I created an implementation for From<Rgb555> and From<Rgb565> that simply converts the value into Rbg888 and use its From implementation to convert the image.
I tested it with this image from the Waveshare repo example that was already converted to the correct color table, and just worked. Of course it needs a better implementation but it works.
