fix trackmap for empty tracks

1 files changed, 13 insertions, 3 deletions

diff --git a/fietsboek/trackmap.py b/fietsboek/trackmap.py
index 994b3dd..4cb13aa 100644
--- a/fietsboek/trackmap.py
+++ b/fietsboek/trackmap.py
@@ -11,6 +11,12 @@ from .views.tileproxy import TileRequester
 
 TILE_SIZE = 256
 
+# This is arbitrarily set to provide some image in case a render is requested
+# for a track without points. I've arbitrarily chosen Berlin as the represented
+# area.
+DEFAULT_ZOOM = 9
+DEFAULT_BBOX = (70062, 70611, 42824, 43179)
+
 
 def to_web_mercator(lat: float, lon: float, zoom: int) -> tuple[int, int]:
     """Convert a pari of latitude/longitude coordinates to web mercator form.
@@ -69,6 +75,9 @@ class TrackMapRenderer:
         return image
 
     def _find_zoom(self) -> tuple[int, tuple[int, int, int, int]]:
+        if not self.track.points:
+            return DEFAULT_ZOOM, DEFAULT_BBOX
+
         for zoom in range(self.maxzoom or 19, 0, -1):
             min_x, max_x = 2**zoom * TILE_SIZE, 0
             min_y, max_y = 2**zoom * TILE_SIZE, 0
@@ -85,7 +94,7 @@ class TrackMapRenderer:
             else:
                 return zoom, (min_x, max_x, min_y, max_y)
 
-        return 1, (0, 512, 0, 512)
+        return DEFAULT_ZOOM, DEFAULT_BBOX
 
     def _draw_base(self, image, zoom, bbox):
         min_x, max_x, min_y, max_y = bbox
@@ -115,8 +124,9 @@ class TrackMapRenderer:
         )
         coords = [(x - start_x, y - start_y) for x, y in coords]
 
-        draw = ImageDraw.Draw(image)
-        draw.line(coords, fill=self.color, width=self.line_width, joint="curve")
+        if coords:
+            draw = ImageDraw.Draw(image)
+            draw.line(coords, fill=self.color, width=self.line_width, joint="curve")
 
 
 def render(