add GEE exporter

Author: kovaca

src/palettize/exporters/__init__.py

@@ -13,6 +13,7 @@
 from .titiler import TitilerExporter
 from .mapgl import MapglExporter
 from .observable_plot import ObservablePlotExporter
+from .gee import GEEExporter
 
 # Global registry for exporters
 # Maps an identifier string to an instantiated exporter object or a callable that returns one.
@@ -84,6 +85,7 @@ def list_available_exporters() -> Dict[str, str]:
     TitilerExporter(),
     MapglExporter(),
     ObservablePlotExporter(),
+    GEEExporter(),
 ]
 
 for exporter_instance in _BUILTIN_EXPORTERS:

src/palettize/exporters/gee.py

@@ -0,0 +1,109 @@
+"""Exporter for Google Earth Engine (GEE)."""
+
+from typing import Any, Dict, Optional
+
+from palettize.core import Colormap, ScalingFunction
+from ._base import BaseExporter
+
+
+class GEEExporter(BaseExporter):
+    """
+    Exporter for Google Earth Engine JavaScript code snippets.
+    """
+
+    @property
+    def identifier(self) -> str:
+        return "gee"
+
+    @property
+    def name(self) -> str:
+        return "Google Earth Engine Snippet"
+
+    @property
+    def default_file_extension(self) -> str:
+        return "js"
+
+    def export(
+        self,
+        colormap: Colormap,
+        scaler: ScalingFunction,
+        domain_min: float,
+        domain_max: float,
+        options: Optional[Dict[str, Any]] = None,
+    ) -> str:
+        """
+        Exports the colormap to a GEE JavaScript snippet.
+
+        Accepted options:
+            type (str): 'default' or 'sld'. Default is 'default'.
+            num_colors (int): Number of color steps to generate. Default 256.
+        """
+        options = options or {}
+        export_type = options.get("type", "default")
+        num_colors = options.get("num_colors", 256)
+        if not isinstance(num_colors, int):
+            raise ValueError("Option 'num_colors' must be an integer.")
+
+        if export_type == "default":
+            return self._export_default(colormap, domain_min, domain_max, num_colors)
+        elif export_type == "sld":
+            return self._export_sld(colormap, domain_min, domain_max, num_colors)
+        else:
+            raise ValueError(f"Unsupported GEE export type: {export_type}")
+
+    def _export_default(self, colormap: Colormap, domain_min: float, domain_max: float, num_colors: int) -> str:
+        """Exports a GEE visualization palette."""
+        if num_colors < 2:
+            raise ValueError("Number of colors must be at least 2.")
+        
+        # GEE palette colors are hex strings without the '#'
+        colors = []
+        for i in range(num_colors):
+            position = i / (num_colors - 1)
+            color_hex = colormap.get_color(position, output_format="hex")
+            if isinstance(color_hex, str):
+                colors.append(color_hex[1:])
+
+        palette_str = ", ".join([f"'{c}'" for c in colors])
+        return f"var palettize_viz = {{min: {domain_min}, max: {domain_max}, palette: [{palette_str}]}};"
+
+    def _export_sld(self, colormap: Colormap, domain_min: float, domain_max: float, num_colors: int) -> str:
+        """Exports a GEE SLD-style palette."""
+        if num_colors < 2:
+            raise ValueError("Number of colors must be at least 2 for SLD ramp.")
+
+        entries = []
+        for i in range(num_colors):
+            position = i / (num_colors - 1)
+            
+            value = domain_min + position * (domain_max - domain_min)
+            # a bit of rounding to avoid long float strings
+            if abs(value - round(value)) < 1e-9:
+                value = int(round(value))
+            else:
+                value = round(value, 4)
+
+            color_hex_any = colormap.get_color(position, output_format="hex")
+            if isinstance(color_hex_any, str):
+                color_hex = color_hex_any
+            else:
+                color_hex = "#000000" # Fallback, should not be reached with hex format
+            # Each entry is a JS string literal concatenated with '+'
+            entry = f'      \'<ColorMapEntry color="{color_hex}" quantity="{value}" label="{value}" />\' +'
+            entries.append(entry)
+
+        # remove the last ' +' from the last entry
+        if entries:
+            entries[-1] = entries[-1].rstrip(" +")
+
+        entries_str = "\n".join(entries)
+
+        # Using a multiline f-string for better readability and correctness
+        final_string = f"""var palettize_sld =
+  '<RasterSymbolizer>' +
+    '<ColorMap type="ramp" extended="false" >' +
+{entries_str}
+    '</ColorMap>' +
+  '</RasterSymbolizer>';"""
+        
+        return final_string