lib8: interpolate: add lerp8by8 and map8 functions

src/lib8/interpolate.rs

@@ -82,6 +82,25 @@ pub fn lerp7by8(a: i8, b: i8, frac: u8) -> i8 {
     }
 }
 
+pub fn lerp8by8(a: u8, b: u8, frac: u8) -> u8 {
+    if b > a {
+        let delta = b - a;
+        let scaled = scale8(delta, frac);
+        return a + scaled;
+    } else {
+        let delta = a - b;
+        let scaled = scale8(delta, frac);
+        return a - scaled;
+    }
+}
+
+pub fn map8(x: u8, range_start: u8, range_end: u8) -> u8 {
+    let range_width = range_end - range_start;
+    let mut out = scale8(x, range_width);
+    out += range_start;
+    return out;
+}
+
 pub fn ease8InOutQuad(i: u8) -> u8 {
     let j = if i & 0x80 != 0 {
         255 - i