feat: Implement Google Earth Engine palette external (#82)

* Implement Google Earth Engine palette external

* linting

---------

Co-authored-by: Talley Lambert <[email protected]>

Author: SiggyF

README.md

@@ -102,6 +102,7 @@ third-party colormap objects, including:
 - [plotly](https://plotly.com/python/)
 - [bokeh](https://docs.bokeh.org/en/latest/)
 - [altair](https://altair-viz.github.io/)
+- [earthengine-api](https://developers.google.com/earth-engine/guides/quickstart_python)
 - [pyqtgraph](https://www.pyqtgraph.org/)
 
 See [documentation](https://cmap-docs.readthedocs.io/en/latest/colormaps/#usage-with-external-visualization-libraries)

docs/colormaps.md

@@ -368,6 +368,13 @@ external visualization libraries.  To that end, `cmap.Colormap` provides
 
     Returns a list of hexadecimal color strings.
 
+- [gee](https://developers.google.com/earth-engine/guides/quickstart_python)
+
+    ```python
+    Colormap("viridis").to_gee()
+    ```
+    Returns a list of hexadecimal color strings (without a `#` prefix).
+
 - [pyqtgraph](https://pyqtgraph.org/)
 
     ```python

src/cmap/_colormap.py

@@ -744,6 +744,15 @@ def to_altair(self, N: int = 256) -> list[str]:
         """
         return _external.to_altair(self, N=N)
 
+    def to_gee(self, N: int = 256) -> list[str]:
+        """Return a Google Earth Engine palette with N color samples from the colormap.
+
+        Suitable for passing to the palette parameter of Google Earth Engine
+        visualizations. See:
+        https://developers.google.com/earth-engine/guides/image_visualization
+        """
+        return _external.to_gee(self, N=N)
+
     def to_viscm(
         self, dpi: int = 100, dest: str | None = None
     ) -> matplotlib.figure.Figure:

src/cmap/_external.py

@@ -106,6 +106,22 @@ def to_altair(cm: Colormap, N: int = 256) -> list[str]:
     return [color.hex for color in cm.iter_colors(N)]
 
 
+def to_gee(cm: Colormap, N: int = 256) -> list[str]:
+    """Return a Google Earth Engine palette with N color samples from the colormap.
+
+    Suitable for passing to the palette parameter of Google Earth Engine visualizations.
+
+    See details at
+    https://developers.google.com/earth-engine/guides/image_visualization#color-palettes
+    """
+    rgbs = [
+        # drop the # symbol
+        color.hex.lstrip("#")
+        for color in cm.iter_colors(N)
+    ]
+    return rgbs
+
+
 def to_pyqtgraph(cm: Colormap) -> PyqtgraphColorMap:
     """Return a `pyqtgraph.Colormap`."""
     from pyqtgraph import ColorMap

tests/test_third_party.py

@@ -147,6 +147,16 @@ def test_altair() -> None:
     assert alt[-1] == "#0000FF"
 
 
+def test_gee() -> None:
+    # These strings are used in the palette variables
+    # You can't test this without an account
+    cmap1 = Colormap(["red", "green", "blue"])
+    alt = cmap1.to_gee()
+    assert isinstance(alt, list) and all(isinstance(c, str) for c in alt)
+    assert alt[0] == "FF0000"
+    assert alt[-1] == "0000FF"
+
+
 def test_viscm(tmp_path: Path) -> None:
     pytest.importorskip("viscm")
     # NOT using importorskip here because there IS an error import viscm