Work around latest projection issues with new proj library and mapnik

See also e.g. mapnik/python-mapnik#246
hholzgra · Mar 27, 2024 · c72bd43 · c72bd43
1 parent 7f55ad3
commit c72bd43
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Showing 3 changed files with 21 additions and 13 deletions.
diff --git a/ocitysmap/coords.py b/ocitysmap/coords.py
@@ -33,11 +33,6 @@
     "Mapnik module version %s is too old, see ocitysmap's INSTALL " \
     "for more details." % mapnik.mapnik_version_string()
 
-_MAPNIK_PROJECTION = "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 " \
-                     "+lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m   " \
-                     "+nadgrids=@null +no_defs +over"
-
-
 EARTH_RADIUS = 6370986 # meters
 
 def dd2dms(value):
@@ -49,6 +44,20 @@ def dd2dms(value):
 
     return (degrees, minutes, seconds)
 
+def get_proj_transformation():
+    try:
+        # new Proj library versions (e.g. v9 on Debian 12)
+        proj_wgs84  = mapnik.Projection("epsg:4326") 
+        proj_google = mapnik.Projection("epsg:3857")
+    except:
+        # old Proj libraray versions (e.g. v7 on Debian 11)
+        proj_wgs84  = mapnik.Projection("+init=epsg:4326")
+        proj_google = mapnik.Projection( "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 " \
+                                         "+lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m   " \
+                                         "+nadgrids=@null +no_defs +over")
+
+    return mapnik.ProjTransform(proj_wgs84, proj_google)
+
 class Point:
     def __init__(self, lat, long_):
         self._lat, self._long = float(lat), float(long_)
@@ -299,7 +308,7 @@ def to_mercator(self):
                                 self.get_top_left()[0],
                                 self.get_bottom_right()[1],
                                 self.get_bottom_right()[0])
-        _proj = mapnik.Projection(_MAPNIK_PROJECTION)
+        _proj = get_proj_transformation()
         bottom_left = _proj.forward(mapnik.Coord(envelope.minx, envelope.miny))
         top_right = _proj.forward(mapnik.Coord(envelope.maxx, envelope.maxy))
         top_left = mapnik.Coord(bottom_left.x, top_right.y)

diff --git a/ocitysmap/layoutlib/multi_page_renderer.py b/ocitysmap/layoutlib/multi_page_renderer.py
@@ -157,10 +157,9 @@ def __init__(self, db, rc, tmpdir, dpi, file_prefix):
         OVERLAP_MARGIN_MM = 20
 
         # Convert the original Bounding box into Mercator meters
-        self._proj = mapnik.Projection(coords._MAPNIK_PROJECTION)
+        self._proj = coords.get_proj_transformation()
         orig_envelope = self._project_envelope(self.rc.bounding_box)
 
-
         while True:
             # Extend the bounding box to take into account the lost outer
             # margin
@@ -593,8 +592,8 @@ def _inverse_envelope(self, envelope):
         Inverse the given cartesian envelope (in 3587) back to a 4326
         bounding box.
         """
-        c0 = self._proj.inverse(mapnik.Coord(envelope.minx, envelope.miny))
-        c1 = self._proj.inverse(mapnik.Coord(envelope.maxx, envelope.maxy))
+        c0 = self._proj.backward(mapnik.Coord(envelope.minx, envelope.miny))
+        c1 = self._proj.backward(mapnik.Coord(envelope.maxx, envelope.maxy))
         return coords.BoundingBox(c0.y, c0.x, c1.y, c1.x)
 
     def _prepare_page(self, ctx):

diff --git a/ocitysmap/maplib/map_canvas.py b/ocitysmap/maplib/map_canvas.py
@@ -65,7 +65,7 @@ def __init__(self, stylesheet, bounding_box, _width, _height, dpi=72.0,
         """
 
         self._style_name = stylesheet.name
-        self._proj = mapnik.Projection(_MAPNIK_PROJECTION)
+        self._proj = ocitysmap.coords.get_proj_transformation()
         self._dpi  = dpi
 
         # This is where the magic of the map canvas happens. Given an original
@@ -211,8 +211,8 @@ def _project_envelope(self, bbox):
     def _inverse_envelope(self, envelope):
         """Inverse the given cartesian envelope (in 3587) back to a 4326
         bounding box."""
-        c0 = self._proj.inverse(mapnik.Coord(envelope.minx, envelope.miny))
-        c1 = self._proj.inverse(mapnik.Coord(envelope.maxx, envelope.maxy))
+        c0 = self._proj.backward(mapnik.Coord(envelope.minx, envelope.miny))
+        c1 = self._proj.backward(mapnik.Coord(envelope.maxx, envelope.maxy))
         return ocitysmap.coords.BoundingBox(c0.y, c0.x, c1.y, c1.x)
 
 if __name__ == '__main__':