4. Multimodal Table Scanning Application

1. Concept Introduction

1.1 What is "Multimodal Table Scanning"?

Multimodal table scanning is a technology that uses image processing and artificial intelligence to identify and extract table information from images or PDF documents. It not only focuses on visual table structure recognition but also combines text content, layout information, and other multimodal data to enhance table understanding. Large Language Models (LLMs) provide powerful semantic analysis capabilities for understanding these extracted information, complementing each other to jointly improve the intelligence level of document processing.

1.2 Brief Implementation Principle

1. Table Detection and Content Recognition

   • Use computer vision technology to locate tables in documents and convert text within tables into editable format through OCR technology.
   • Use deep learning methods to parse table structure (row/column division, merged cells, etc.), generating structured data representation.

2. Multimodal Fusion

   • Integrate visual (such as table layout), text (OCR results), and possibly existing metadata (such as file type, source) to form a comprehensive data view.
   • Use specially designed multimodal models (such as LayoutLM) to simultaneously process these different types of data to more accurately understand table content and its contextual relationships.

2. Code Analysis

Key Code

1. Tool Layer Entry (largemodel/utils/tools_manager.py)

The scan_table function in this file defines the execution flow of this tool, specifically how it constructs a Prompt that requires returning Markdown format.

​x
# From largemodel/utils/tools_manager.py
class ToolsManager:
    # ...
    def scan_table(self, args):
        """
        Scan a table from an image and save the content as a Markdown file.
​
        :param args: Arguments containing the image path.
        :return: Dictionary with file path and content.
        """
        self.node.get_logger().info(f"Executing scan_table() tool with args: {args}")
        try:
            image_path = args.get("image_path")
            # ... (Path checking and fallback)
​
            # Construct a prompt asking the large model to recognize the table and return it in Markdown format.
            if self.node.language == 'zh':
                prompt = "Please carefully analyze this image, identify the table within it, and return its content in Markdown format."
            else:
                prompt = "Please carefully analyze this image, identify the table within it, and return its content in Markdown format."
​
            result = self.node.model_client.infer_with_image(image_path, prompt)
            
            # ... (Extract Markdown text from result)
​
            # Save the recognized content to a Markdown file.
            md_file_path = os.path.join(self.node.pkg_path, "resources_file", "scanned_tables", f"table_{timestamp}.md")
            with open(md_file_path, 'w', encoding='utf-8') as f:
                f.write(table_content)
​
            return {
                "file_path": md_file_path,
                "table_content": table_content
            }
        # ... (Error handling)

2. Model Interface Layer (largemodel/utils/large_model_interface.py)

The infer_with_image function in this file is the unified entry point for all image-related tasks.

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# From largemodel/utils/large_model_interface.py
​
class model_interface:
    # ...
    def infer_with_image(self, image_path, text=None, message=None):
        """Unified image inference interface."""
        # ... (Prepare message)
        try:
            # Decide which specific implementation to call based on the value of self.llm_platform
            if self.llm_platform == 'ollama':
                response_content = self.ollama_infer(self.messages, image_path=image_path)
            elif self.llm_platform == 'tongyi':
                # ... Logic for calling Tongyi model
                pass
            # ... (Logic for other platforms)
        # ...
        return {'response': response_content, 'messages': self.messages.copy()}

Code Analysis

The table scanning function is a typical application that converts unstructured image data into structured text data. Its core technology is still guiding model behavior through Prompt Engineering.

1. Tool Layer (tools_manager.py):

   • The scan_table function is the business process controller for this feature. It receives an image containing a table as input.
   • The most critical operation of this function is building a goal-oriented Prompt. This Prompt directly instructs the large model to perform two tasks: 1. Identify the table in the image. 2. Return the identified content in Markdown format. This mandatory requirement for output format is key to achieving unstructured to structured conversion.
   • After building the Prompt, it calls the infer_with_image method of the model interface layer, passing both the image and this formatting instruction.
   • After receiving the returned Markdown text from the model interface layer, it performs a file operation: writing this text content into a new .md file.
   • Finally, it returns structured data containing the new file path and table content.

2. Model Interface Layer (large_model_interface.py):

   • The infer_with_image function continues to serve as the unified "dispatch center". It receives the image and Prompt from scan_table, and dispatches tasks to the correct backend model implementation based on the current system configuration (self.llm_platform).
   • Regardless of the backend model, the task of this layer is to handle communication details with specific platforms, ensuring that image and text data are sent correctly, and then returning the plain text returned by the model (here it's Markdown formatted text) to the tool layer.

In summary, the general flow of table scanning is: ToolsManager receives the image and builds a "convert the table in this image to Markdown" instruction -> ToolsManager calls the model interface -> model_interface packages the image and this instruction, and sends it to the corresponding model platform based on configuration -> Model returns Markdown formatted text -> model_interface returns the text to ToolsManager -> ToolsManager saves the text as a .md file and returns the result. This flow demonstrates how to use the format-following capability of large models to use them as powerful OCR (Optical Character Recognition) and data structuring tools.

3. Practical Operations

3.1 Configure Online LLM

1. First obtain API Key from OpenRouter platform

2. Then update the key in the configuration file, open the model interface configuration file large_model_interface.yaml:

   xxxxxxxxxx
   vim ~/yahboom_ws/src/largemodel/config/large_model_interface.yaml
   

3. Enter your API Key: Find the corresponding section and paste the API Key you just copied. Here we use Tongyi Qianwen configuration as an example

   xxxxxxxxxx
   # large_model_interface.yaml
   ​
   # OpenRouter platform configuration
   openrouter_api_key: "sk-xxxxxxxxxxxxxxxxxxxxxxxxxxxx"
   openrouter_model: "nvidia/nemotron-nano-12b-v2-vl:free" # Model to use, e.g., "google/gemini-pro-vision"
   

4. Open the main configuration file yahboom.yaml:

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   vim ~/yahboom_ws/src/largemodel/config/yahboom.yaml
   

5. Select the online platform to use: Modify the llm_platform parameter to the platform name you want to use

   xxxxxxxxxx
   # yahboom.yaml
   ​
   model_service:
     ros__parameters:
       # ...
       llm_platform: 'openrouter'              # Currently selected large model platform 
       # Available platforms: 'ollama','openrouter'
   

Recompile

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cd ~/yahboom_ws/
colcon build
source install/setup.bash

3.2 Start and Test Function

1. Prepare table image file:

   Place a test table image file in the following path: /home/sunrise/yahboom_ws/src/largemodel/resources_file/scan_table

   Then rename the image to test_table.jpg

2. Start the largemodel main program:

   Open a terminal, then run the following command：

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   ros2 launch largemodel largemodel_control.launch.py text_chat_mode:=true
   

3. Send text commands: Open another terminal and run the following command，

   xxxxxxxxxx
   ros2 run text_chat text_chat
   

   Then start typing text: "Analyze the table".

4. Observe results: In the first terminal running the main program, you will see log output showing that the system received the command, called the scan_table tool, prompted that scan_table execution is complete, and saved the scanned information to the document.

   We can find this document in the ~/yahboom_ws/src/largemodel/resources_file/scan_table path.