add color lerping

1 files changed, 34 insertions, 0 deletions

diff --git a/algorithms.py b/algorithms.py
index 6e01287..8a6e2d3 100644
--- a/algorithms.py
+++ b/algorithms.py
@@ -1,3 +1,4 @@
+import colorsys
 import heapq
 import math
 
@@ -16,6 +17,39 @@ def length_haversine(p1, p2):
     return 6372797.560856 * c  # return the distance in meters
 
 
+def chunks(lst, n):
+    """ Split lst into chunks of size n.
+
+    The final chunk will have size equal to len(lst) % n
+    """
+    for i in range(0, len(lst), n):
+        yield lst[i:min(i+n, len(lst))]
+
+
+def lerp_color(start_color, end_color, t):
+    """ Lerp between two colors by a factor t.
+
+    Colors are assumed to be in the form "#RRGGBB"
+    """
+    def lerp(a, b, t):
+        return a + (b - a) * t
+
+    start = [int(c, 16)/255 for c in chunks(start_color[1:], 2)]
+    end = [int(c, 16)/255 for c in chunks(end_color[1:], 2)]
+
+    start = colorsys.rgb_to_hsv(*start)
+    end = colorsys.rgb_to_hsv(*end)
+
+    color = [lerp(c1, c2, t) for (c1, c2) in zip(start, end)]
+    color = colorsys.hsv_to_rgb(*color)
+
+    return "#{:02x}{:02x}{:02x}".format(
+        int(color[0] * 255),
+        int(color[1] * 255),
+        int(color[2] * 255),
+    )
+
+
 def get_closest_node_id(nodes, source_node):
     """ Search through all nodes and return the id of the node
     that is closest to 'source_node'. """