add alpha component

src/durandal/image.rs

@@ -62,6 +62,7 @@ pub trait Color
    fn r(&self) -> Self::Output;
    fn g(&self) -> Self::Output;
    fn b(&self) -> Self::Output;
+   fn a(&self) -> Self::Output;
 }
 
 impl Image16
@@ -126,7 +127,7 @@ impl Color16
 {
    pub const fn new(r: u16, g: u16, b: u16) -> Color16
    {
-      Color16(r, g, b)
+      Color16(r, g, b, u16::max_value())
    }
 }
 
@@ -149,13 +150,18 @@ impl Color for Color16
    {
       self.2
    }
+
+   fn a(&self) -> u16
+   {
+      self.3
+   }
 }
 
 impl Color8
 {
    pub const fn new(r: u8, g: u8, b: u8) -> Color8
    {
-      Color8(r, g, b)
+      Color8(r, g, b, u8::max_value())
    }
 }
 
@@ -178,15 +184,20 @@ impl Color for Color8
    {
       self.2
    }
+
+   fn a(&self) -> u8
+   {
+      self.3
+   }
 }
 
 /// A RGB16 color.
 #[derive(Clone, Debug, PartialEq)]
-pub struct Color16(u16, u16, u16);
+pub struct Color16(u16, u16, u16, u16);
 
 /// A RGB8 color.
 #[derive(Clone, Debug, PartialEq)]
-pub struct Color8(u8, u8, u8);
+pub struct Color8(u8, u8, u8, u8);
 
 /// RGB16 image.
 pub struct Image16