Add programmatic export API

README.md

@@ -166,6 +166,18 @@ walker = pyg.walk(
 * [Use PyGWalker in Kaggle](https://www.kaggle.com/code/lxy21495892/airbnb-eda-pygwalker-demo)
 * [Use PyGWalker in Google Colab](https://colab.research.google.com/drive/171QUQeq-uTLgSj1u-P9DQig7Md1kpXQ2?usp=sharing)
 
+### Programmatic Export of Charts
+
+After saving a chart from the UI, you can retrieve the image directly from Python.
+
+```python
+walker = pyg.walk(df, spec="./chart_meta_0.json")
+# edit the chart in the UI and click the save button
+walker.save_chart_to_file("Chart 1", "chart1.svg", save_type="svg")
+png_bytes = walker.export_chart_png("Chart 1")
+svg_bytes = walker.export_chart_svg("Chart 1")
+```
+
 ## Use pygwalker in Streamlit
 Streamlit allows you to host a web version of pygwalker without figuring out details of how web application works.
 

pygwalker/api/pygwalker.py

@@ -274,7 +274,7 @@ def chart_list(self) -> List[str]:
         """
         return list(self._chart_map.keys())
 
-    def save_chart_to_file(self, chart_name: str, path: str, save_type: Literal["html", "png"] = "png"):
+    def save_chart_to_file(self, chart_name: str, path: str, save_type: Literal["html", "png", "svg"] = "png"):
         """
         Save the chart to a file.
         """
@@ -286,8 +286,12 @@ def save_chart_to_file(self, chart_name: str, path: str, save_type: Literal["htm
             content = self.export_chart_png(chart_name)
             write_mode = "wb"
             encoding = None
+        elif save_type == "svg":
+            content = self.export_chart_svg(chart_name)
+            write_mode = "wb"
+            encoding = None
         else:
-            raise ValueError(f"save_type must be html or png, but got {save_type}")
+            raise ValueError(f"save_type must be html, png or svg, but got {save_type}")
 
         with open(path, write_mode, encoding=encoding) as f:
             f.write(content)
@@ -311,6 +315,20 @@ def export_chart_png(self, chart_name: str) -> bytes:
         with urllib.request.urlopen(chart_data.single_chart) as png_string:
             return png_string.read()
 
+    def export_chart_svg(self, chart_name: str) -> bytes:
+        """Export the chart as svg bytes."""
+        chart_data = self._get_chart_by_name(chart_name)
+        if len(chart_data.charts) == 0:
+            raise ValueError(f"chart_name: {chart_name} has no svg data")
+        svg_str = chart_data.charts[0].data
+        prefix = "data:image/svg+xml;base64,"
+        if isinstance(svg_str, str) and svg_str.startswith(prefix):
+            import base64
+            return base64.b64decode(svg_str[len(prefix):])
+        if isinstance(svg_str, str):
+            return svg_str.encode("utf-8")
+        return svg_str
+
     def display_chart(self, chart_name: str, *, title: Optional[str] = None, desc: str = ""):
         """
         Display the chart in the notebook.