Legend order is now deterministic (#143)

Author: timtreis

CHANGELOG.md

@@ -8,6 +8,14 @@ and this project adheres to [Semantic Versioning][].
 [keep a changelog]: https://keepachangelog.com/en/1.0.0/
 [semantic versioning]: https://semver.org/spec/v2.0.0.html
 
+## [0.0.5] -tbd
+
+### Added
+
+### Fixed
+
+-   Legend order is now deterministic (#143)
+
 ## [0.0.4] - 2023-08-11
 
 ### Fixed

src/spatialdata_plot/pl/render.py

@@ -180,7 +180,8 @@ def _get_collection_shape(
     )
     cax = ax.add_collection(_cax)
 
-    palette = ListedColormap(set(color_vector)) if render_params.palette is None else render_params.palette
+    # Using dict.fromkeys here since set returns in arbitrary order
+    palette = ListedColormap(dict.fromkeys(color_vector)) if render_params.palette is None else render_params.palette
 
     _ = _decorate_axs(
         ax=ax,

src/spatialdata_plot/pl/utils.py

@@ -838,11 +838,11 @@ def _get_palette(
 
     if isinstance(palette, str):
         cmap = plt.get_cmap(palette)
-        palette = [to_hex(x) for x in cmap(np.linspace(0, 1, len_cat), alpha=alpha)]
     elif isinstance(palette, ListedColormap):
-        palette = [to_hex(x) for x in palette(np.linspace(0, 1, len_cat), alpha=alpha)]
+        cmap = palette
     else:
         raise TypeError(f"Palette is {type(palette)} but should be string or `ListedColormap`.")
+    palette = [to_hex(np.round(x, 5)) for x in cmap(np.linspace(0, 1, len_cat), alpha=alpha)]
 
     return dict(zip(categories, palette))