Add harmonize utils

src/analysis/mapping.rs

@@ -122,12 +122,15 @@ impl ColorMappings {
         self.0.last_mut().unwrap().target = target;
     }
 
-    pub fn apply_rgba(&self, rgba: &[u8]) -> Vec<u8> {
-        let lookup: HashMap<_, _> = self
-            .0
+    pub fn lookup(&self) -> HashMap<[u8; 3], [u8; 3]> {
+        self.0
             .iter()
             .flat_map(|entry| entry.members.iter().map(move |&rgb| (rgb, entry.target)))
-            .collect();
+            .collect()
+    }
+
+    pub fn apply_rgba(&self, rgba: &[u8]) -> Vec<u8> {
+        let lookup = self.lookup();
         let mut output = rgba.to_vec();
         for pixel in output.as_chunks_mut::<4>().0 {
             if pixel[3] != 0