Add base64 API endpoint for programmatic access

- digitize_chart now accepts both PIL Image and base64 strings
- Add /api/digitize_base64 endpoint using gr.Textbox inputs
so external clients can send base64 without Gradio file upload

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

api_server.py

@@ -33,10 +33,12 @@ import cv2
 import numpy as np
 import json
 import io
+import base64
 import zipfile
 import urllib.request
 import ssl
 import gradio as gr
+from PIL import Image
 from datetime import datetime, timezone
 
 # ============================================================
@@ -323,8 +325,17 @@ def digitize_chart(
     if image is None:
         return json.dumps({"error": "No image provided"})
 
-    # Convert PIL Image to BGR numpy array
-    img_rgb = np.array(image)
+    # Accept both PIL Image and base64 string
+    if isinstance(image, str):
+        # Strip data URI prefix if present (e.g. "data:image/png;base64,...")
+        if "," in image:
+            image = image.split(",", 1)[1]
+        img_bytes = base64.b64decode(image)
+        pil_img = Image.open(io.BytesIO(img_bytes)).convert("RGB")
+        img_rgb = np.array(pil_img)
+    else:
+        img_rgb = np.array(image)
+
     img_bgr = cv2.cvtColor(img_rgb, cv2.COLOR_RGB2BGR)
 
     # Extract lines
@@ -433,6 +444,28 @@ def create_app():
             outputs=[output, file_output],
         )
 
+        # Programmatic API endpoint that accepts base64 string directly
+        # This avoids Gradio's file upload requirement for gr.Image
+        api_image_input = gr.Textbox(visible=False)
+        api_auto_axis = gr.Checkbox(value=True, visible=False)
+        api_downsample = gr.Textbox(value="arc_length", visible=False)
+        api_max_pts = gr.Number(value=20, visible=False)
+        api_fixed_stp = gr.Number(value=10, visible=False)
+        api_sort = gr.Textbox(value="mean_y_desc", visible=False)
+        api_out_fmt = gr.Textbox(value="starry_digitizer_json", visible=False)
+        api_output = gr.Textbox(visible=False)
+
+        def api_digitize(image_base64, auto_axis, downsample, max_pts, fixed_stp, sort, out_fmt):
+            return digitize_chart(image_base64, auto_axis, downsample, int(max_pts), int(fixed_stp), sort, out_fmt)
+
+        api_btn = gr.Button(visible=False, elem_id="api_btn")
+        api_btn.click(
+            fn=api_digitize,
+            inputs=[api_image_input, api_auto_axis, api_downsample, api_max_pts, api_fixed_stp, api_sort, api_out_fmt],
+            outputs=[api_output],
+            api_name="digitize_base64",
+        )
+
     return demo