progress

gpx-rs/src/algorithm/simplify.rs

@@ -0,0 +1,65 @@
+use crate::gpx::{TrackSegment, TrackSegmentIndex};
+
+pub fn ramer_douglas_peucker<F, T>(
+    trkseg: &TrackSegment,
+    distance: &F,
+    epsilon: T,
+) -> Vec<TrackSegmentIndex>
+where
+    F: Fn(TrackSegmentIndex, TrackSegmentIndex, TrackSegmentIndex) -> T,
+    T: Default + PartialOrd + Copy,
+{
+    match trkseg.len() {
+        0 => vec![],
+        1 => vec![trkseg.first_index().unwrap()],
+        2 => vec![trkseg.last_index().unwrap()],
+        _ => {
+            let first = trkseg.first_index().unwrap();
+            let last = trkseg.last_index().unwrap();
+
+            let mut indices = vec![first];
+            ramer_douglas_peucker_helper(trkseg, first, last, distance, epsilon, &mut indices);
+            indices.push(last);
+            indices
+        }
+    }
+}
+
+fn ramer_douglas_peucker_helper<F, T>(
+    trkseg: &TrackSegment,
+    start: TrackSegmentIndex,
+    end: TrackSegmentIndex,
+    distance: &F,
+    epsilon: T,
+    indices: &mut Vec<TrackSegmentIndex>,
+) where
+    F: Fn(TrackSegmentIndex, TrackSegmentIndex, TrackSegmentIndex) -> T,
+    T: Default + PartialOrd + Copy,
+{
+    let mut max_idx = None;
+    let mut max_dist = T::default();
+
+    let mut cur = trkseg.next_index(Some(start));
+
+    while let Some(idx) = cur {
+        if idx == end {
+            break;
+        }
+
+        let dist = distance(start, end, idx);
+        if dist > max_dist {
+            max_idx = Some(idx);
+            max_dist = dist;
+        }
+
+        cur = trkseg.next_index(cur);
+    }
+
+    if let Some(idx) = max_idx {
+        if max_dist > epsilon {
+            ramer_douglas_peucker_helper(trkseg, start, idx, distance, epsilon, indices);
+            indices.push(idx);
+            ramer_douglas_peucker_helper(trkseg, idx, end, distance, epsilon, indices);
+        }
+    }
+}