Transparent background

[mys721tx]

Currently, all transparency are hardcoded to 0xff:

silicon/src/utils.rs

Lines 27 to 32 in c277f1a

	Ok(Rgba([
	((rgb >> 16) & 0xff) as u8,
	((rgb >> 8) & 0xff) as u8,
	(rgb & 0xff) as u8,
	0xff,
	]))

There should be a switch to toggle the background transparency so that the output image can be readily used without concerns of background color.

I can think of are two way to implement this:

1. Change the RGBA parsing so that the alpha will also be parsed. This may involves extra handling of RGB string. This may allow transparent theme in the future.
2. Create a new boolean argument so that it will override the alpha setting in Config.background. This likely will involve some processing outside of the struct declaration.

I would like to invite comments from everyone for how to proceed.

[Aloxaf]

I'd like to choose the first way. But I'm not sure whether it will affect the other function of silicon. Silicon should have some tests.

BTW, the transparent theme is already supported (if there are)

silicon/src/utils.rs

Lines 36 to 41 in 4ea9203

	impl ToRgba for syntect::highlighting::Color {
	type Target = Rgba<u8>;
	fn to_rgba(&self) -> Self::Target {
	Rgba([self.r, self.g, self.b, self.a])
	}
	}

[AndydeCleyre]

BTW, the transparent theme is already supported (if there are)

As in, it's possible to have a theme where the fake window is transparent, revealing the image background behind?

Are there any known themes which do this?