lib8: interpolate: provide a trait to handle fract8 operations

src/lib8/interpolate.rs

@@ -1,8 +1,19 @@
 use num::PrimInt;
 
-pub fn scale8(i: u8, scale: u8) -> u8 {
+type Fract8 = u8;
+pub trait Fract8Ops {
+    fn scale8(self, scale: Fract8) -> Self;
+}
+
+impl Fract8Ops for u8 {
+    fn scale8(self, scale: Fract8) -> Self {
         // borrowed from FastLED
-    (i as u16 * scale as u16).wrapping_shr(8) as u8
+        (self as u16 * (1 + scale as u16)).unsigned_shr(8) as u8
+    }
+}
+
+pub fn scale8<T: Fract8Ops>(i: T, scale: Fract8) -> T {
+    i.scale8(scale)
 }
 
 pub fn avg7(i: i8, j: i8) -> i8 {