Support for custom colormaps (#223)

* Handle serialization and deserialization of Colormap and lists of colors.

* Add List[str]

* Truthy check

* Linting

* Add validation test

* Handle colormaps instances

* Fix truthy issue

---------

Co-authored-by: Bane Sullivan <banesullivan@gmail.com>

Author: lopezvoliver

localtileserver/client.py

@@ -1,8 +1,10 @@
 from collections.abc import Iterable
+import json
 import logging
 import pathlib
 from typing import List, Optional, Union
 
+from matplotlib.colors import Colormap, ListedColormap
 import rasterio
 import requests
 from rio_tiler.io import Reader
@@ -416,7 +418,7 @@ def create_url(self, path: str, client: bool = False):
     def get_tile_url(
         self,
         indexes: Optional[List[int]] = None,
-        colormap: Optional[str] = None,
+        colormap: Optional[Union[str, Colormap, List[str]]] = None,
         vmin: Optional[Union[float, List[float]]] = None,
         vmax: Optional[Union[float, List[float]]] = None,
         nodata: Optional[Union[int, float]] = None,
@@ -446,8 +448,18 @@ def get_tile_url(
         if indexes is not None:
             params["indexes"] = indexes
         if colormap is not None:
-            # make sure palette is valid
-            palette_valid_or_raise(colormap)
+            if isinstance(colormap, ListedColormap):
+                colormap = json.dumps([c for c in colormap.colors])
+            elif isinstance(colormap, Colormap):
+                colormap = json.dumps(
+                    {k: tuple(v.tolist()) for k, v in enumerate(colormap(range(256), 1, 1))}
+                )
+            elif isinstance(colormap, list):
+                colormap = json.dumps(colormap)
+            else:
+                # make sure palette is valid
+                palette_valid_or_raise(colormap)
+
             params["colormap"] = colormap
         if vmin is not None:
             if isinstance(vmin, Iterable) and not isinstance(indexes, Iterable):

localtileserver/tiler/handler.py

@@ -1,7 +1,9 @@
 """Methods for working with images."""
+import json
 import pathlib
 from typing import Dict, List, Optional, Tuple, Union
 
+from matplotlib.colors import Colormap, LinearSegmentedColormap, ListedColormap
 import numpy as np
 import rasterio
 from rasterio.enums import ColorInterp
@@ -150,7 +152,23 @@ def _render_image(
     colormap: Optional[str] = None,
     img_format: str = "PNG",
 ):
-    colormap = cmap.get(colormap) if colormap else None
+    if colormap in cmap.list():
+        colormap = cmap.get(colormap)
+    elif isinstance(colormap, ListedColormap):
+        c = LinearSegmentedColormap.from_list("", colormap.colors, N=256)
+        colormap = {k: tuple(v) for k, v in enumerate(c(range(256), 1, 1))}
+    elif isinstance(colormap, Colormap):
+        colormap = {k: tuple(v) for k, v in enumerate(colormap(range(256), 1, 1))}
+    elif colormap:
+        c = json.loads(colormap)
+        if isinstance(c, list):
+            c = LinearSegmentedColormap.from_list("", c, N=256)
+            colormap = {k: tuple(v) for k, v in enumerate(c(range(256), 1, 1))}
+        else:
+            colormap = {}
+            for key, value in c.items():
+                colormap[int(key)] = tuple(value)
+
     if (
         not colormap
         and len(indexes) == 1

localtileserver/widgets.py

@@ -3,6 +3,7 @@
 from typing import List, Optional, Union
 import warnings
 
+from matplotlib.colors import Colormap
 import rasterio
 
 from localtileserver.client import TileClient, get_or_create_tile_client
@@ -23,7 +24,7 @@ def get_leaflet_tile_layer(
     port: Union[int, str] = "default",
     debug: bool = False,
     indexes: Optional[List[int]] = None,
-    colormap: Optional[str] = None,
+    colormap: Optional[Union[str, Colormap, List[str]]] = None,
     vmin: Optional[Union[float, List[float]]] = None,
     vmax: Optional[Union[float, List[float]]] = None,
     nodata: Optional[Union[int, float]] = None,

tests/baseline/test_custom_colormap[colormap0-None].png

@@ -1,3 +1,4 @@
+from matplotlib.colors import ListedColormap
 import pytest
 
 from .utilities import get_content
@@ -56,6 +57,24 @@ def test_tile_colormap(bahamas, compare, colormap, indexes):
     compare(direct_content)
 
 
+@pytest.mark.parametrize(
+    "colormap,indexes",
+    [
+        (ListedColormap(["red", "blue"]), None),
+        (ListedColormap(["blue", "green"]), 2),
+    ],
+)
+def test_custom_colormap(bahamas, compare, colormap, indexes):
+    # Get a tile over the REST API
+    tile_url = bahamas.get_tile_url(colormap=colormap, indexes=indexes).format(z=8, x=72, y=110)
+    rest_content = get_content(tile_url)
+    # Get tile directly
+    direct_content = bahamas.tile(z=8, x=72, y=110, colormap=colormap, indexes=indexes)
+    # Make sure they are the same
+    assert rest_content == direct_content
+    compare(direct_content)
+
+
 @pytest.mark.parametrize("vmin", [100, [100, 200, 250]])
 def test_tile_vmin(bahamas, compare, vmin):
     url = bahamas.get_tile_url(