Feat: PDF vision figure parser supports reading context (#12416)

### What problem does this PR solve?

PDF vision figure parser supports reading context.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

deepdoc/parser/figure_parser.py

@@ -14,6 +14,7 @@
 #  limitations under the License.
 #
 from concurrent.futures import ThreadPoolExecutor, as_completed
+import logging
 
 from PIL import Image
 
@@ -21,7 +22,8 @@ from common.constants import LLMType
 from api.db.services.llm_service import LLMBundle
 from common.connection_utils import timeout
 from rag.app.picture import vision_llm_chunk as picture_vision_llm_chunk
-from rag.prompts.generator import vision_llm_figure_describe_prompt
+from rag.prompts.generator import vision_llm_figure_describe_prompt, vision_llm_figure_describe_prompt_with_context
+from rag.nlp import append_context2table_image4pdf
 
 
 def vision_figure_parser_figure_data_wrapper(figures_data_without_positions):
@@ -84,20 +86,36 @@ def vision_figure_parser_figure_xlsx_wrapper(images,callback=None, **kwargs):
 def vision_figure_parser_pdf_wrapper(tbls, callback=None, **kwargs):
     if not tbls:
         return []
+    sections = kwargs.get("sections")
+    parser_config = kwargs.get("parser_config", {})
+    context_size = max(0, int(parser_config.get("image_context_size", 0) or 0))
     try:
         vision_model = LLMBundle(kwargs["tenant_id"], LLMType.IMAGE2TEXT)
         callback(0.7, "Visual model detected. Attempting to enhance figure extraction...")
     except Exception:
         vision_model = None
     if vision_model:
+
         def is_figure_item(item):
-            return (
-                isinstance(item[0][0], Image.Image) and
-                isinstance(item[0][1], list)
-            )
+            return isinstance(item[0][0], Image.Image) and isinstance(item[0][1], list)
+
         figures_data = [item for item in tbls if is_figure_item(item)]
+        figure_contexts = []
+        if sections and figures_data and context_size > 0:
+            figure_contexts = append_context2table_image4pdf(
+                sections,
+                figures_data,
+                context_size,
+                return_context=True,
+            )
         try:
-            docx_vision_parser = VisionFigureParser(vision_model=vision_model, figures_data=figures_data, **kwargs)
+            docx_vision_parser = VisionFigureParser(
+                vision_model=vision_model,
+                figures_data=figures_data,
+                figure_contexts=figure_contexts,
+                context_size=context_size,
+                **kwargs,
+            )
             boosted_figures = docx_vision_parser(callback=callback)
             tbls = [item for item in tbls if not is_figure_item(item)]
             tbls.extend(boosted_figures)
@@ -112,6 +130,8 @@ shared_executor = ThreadPoolExecutor(max_workers=10)
 class VisionFigureParser:
     def __init__(self, vision_model, figures_data, *args, **kwargs):
         self.vision_model = vision_model
+        self.figure_contexts = kwargs.get("figure_contexts") or []
+        self.context_size = max(0, int(kwargs.get("context_size", 0) or 0))
         self._extract_figures_info(figures_data)
         assert len(self.figures) == len(self.descriptions)
         assert not self.positions or (len(self.figures) == len(self.positions))
@@ -156,10 +176,25 @@ class VisionFigureParser:
 
         @timeout(30, 3)
         def process(figure_idx, figure_binary):
+            context_above = ""
+            context_below = ""
+            if figure_idx < len(self.figure_contexts):
+                context_above, context_below = self.figure_contexts[figure_idx]
+            if context_above or context_below:
+                prompt = vision_llm_figure_describe_prompt_with_context(
+                    context_above=context_above,
+                    context_below=context_below,
+                )
+                logging.info(f"[VisionFigureParser] figure={figure_idx} context_size={self.context_size} context_above_len={len(context_above)} context_below_len={len(context_below)} prompt=with_context")
+                logging.info(f"[VisionFigureParser] figure={figure_idx} context_above_snippet={context_above[:512]}")
+                logging.info(f"[VisionFigureParser] figure={figure_idx} context_below_snippet={context_below[:512]}")
+            else:
+                prompt = vision_llm_figure_describe_prompt()
+                logging.info(f"[VisionFigureParser] figure={figure_idx} context_size={self.context_size} context_len=0 prompt=default")
             description_text = picture_vision_llm_chunk(
                 binary=figure_binary,
                 vision_model=self.vision_model,
-                prompt=vision_llm_figure_describe_prompt(),
+                prompt=prompt,
                 callback=callback,
             )
             return figure_idx, description_text