Macro retro_pixel::rgba16

macro_rules! rgba16 {
    ($r:expr, $g:expr, $b:expr, $a:expr) => { ... };
}

Builds a u16 value from the given RGBA values.

Each color channel is cast into u16, and then they're combined into a single u16 value (A1_B5_G5_R5). If color channel aren't within the range 0..=31 you'll get some unintentional output. The alpha value is given as a boolean expression, and flips the highest bit on or off.

#[macro_use]
extern crate retro_pixel;

fn main() {
  const TRANSPARENT_BLACK: u16 = rgba16!(0, 0, 0, false);
  const SOLID_WHITE: u16 = rgba16!(31, 0x1F, 31.0, true);
  assert_eq!(TRANSPARENT_BLACK, 0u16);
  assert_eq!(SOLID_WHITE, ::std::u16::MAX);
  // all other outputs depend on what endian the machine is,
  // currently only little endian is supported.
  assert_eq!(rgba16!(31, 0, 0, false), 0b0000000000011111u16);
  assert_eq!(rgba16!(0, 31, 0, false), 0b0000001111100000u16);
  assert_eq!(rgba16!(0, 0, 31, false), 0b0111110000000000u16);
  assert_eq!(rgba16!(0, 0, 0, true),   0b1000000000000000u16);
}