How to Read Table in Documents

by Curtis Chau

Let’s talk about reading tables in documents. Extracting data from tables using plain Tesseract can be challenging, as the text often resides in cells and is sparsely scattered across the document. However, our library is equipped with a machine learning model that has been trained and fine-tuned for detecting and extracting table data accurately.

For simple tables, you can rely on straightforward table detection, while for more complex structures, our exclusive ReadDocumentAdvanced method provides robust results, effectively parsing the table and delivering data.

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First Step:
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Simple Table Example

Setting the ReadDataTables property to true enables table detection using Tesseract. I created a simple table PDF to test this feature, which you can download here: 'simple-table.pdf.'. Simple tables without merged cells can be detected using this method. For more complex tables, please refer to the method described below.

:path=/static-assets/ocr/content-code-examples/how-to/read-table-in-document-with-tesseract.cs
using IronOcr;
using System;
using System.Data;

// Instantiate OCR engine
var ocr = new IronTesseract();

// Enable table detection
ocr.Configuration.ReadDataTables = true;

using var input = new OcrPdfInput("simple-table.pdf");
var result = ocr.Read(input);

// Retrieve the data
var table = result.Tables[0].DataTable;

// Print out the table data
foreach (DataRow row in table.Rows)
{
    foreach (var item in row.ItemArray)
    {
        Console.Write(item + "\t");
    }
    Console.WriteLine();
}
Imports Microsoft.VisualBasic
Imports IronOcr
Imports System
Imports System.Data

' Instantiate OCR engine
Private ocr = New IronTesseract()

' Enable table detection
ocr.Configuration.ReadDataTables = True

Dim input = New OcrPdfInput("simple-table.pdf")
Dim result = ocr.Read(input)

' Retrieve the data
Dim table = result.Tables(0).DataTable

' Print out the table data
For Each row As DataRow In table.Rows
	For Each item In row.ItemArray
		Console.Write(item & vbTab)
	Next item
	Console.WriteLine()
Next row
VB   C#

Complex Table Example

For complex tables, the ReadDocumentAdvanced method handles them beautifully. In this example, we’ll use the 'table.pdf' file.

The ReadDocumentAdvanced method requires the IronOcr.Extensions.AdvancedScan package to be installed alongside the base IronOCR package. Currently, this extension is only available on Windows.

Please note
Using advanced scan on .NET Framework requires the project to run on x64 architecture. Navigate to the project configuration and uncheck the "Prefer 32-bit" option to achieve this. Learn more in the following troubleshooting guide: "Advanced Scan on .NET Framework."

:path=/static-assets/ocr/content-code-examples/how-to/read-table-in-document-with-ml.cs
using IronOcr;
using System.Linq;

// Instantiate OCR engine
var ocr = new IronTesseract();

using var input = new OcrInput();
input.LoadPdf("table.pdf");

// Perform OCR
var result = ocr.ReadDocumentAdvanced(input);

var cellList = result.Tables.First().CellInfos;
Imports IronOcr
Imports System.Linq

' Instantiate OCR engine
Private ocr = New IronTesseract()

Private input = New OcrInput()
input.LoadPdf("table.pdf")

' Perform OCR
Dim result = ocr.ReadDocumentAdvanced(input)

Dim cellList = result.Tables.First().CellInfos
VB   C#

This method separates the text data of the document into two categories: one enclosed by borders and another without borders. For the bordered content, the library further divides it into subsections based on the table's structure. The results are shown below. It is important to note that, since this method focuses on information enclosed by borders, any merged cells spanning multiple rows will be treated as a single cell.

Result

Read Table in Document

Helper Class

In the current implementation, the extracted cells are not yet organized properly. However, each cell contains valuable information such as X and Y coordinates, dimensions, and more. Using this data, we can create a helper class for various purposes. Below are some basic helper methods:

public static class TableProcessor
{
    public static List<CellInfo> OrganizeCellsByCoordinates(List<CellInfo> cells)
    {
        // Sort cells by Y (top to bottom), then by X (left to right)
        var sortedCells = cells
            .OrderBy(cell => cell.CellRect.Y)
            .ThenBy(cell => cell.CellRect.X)
            .ToList();

        return sortedCells;
    }

    // Example of how to use the function
    public static void ProcessTables(Tables tables)
    {
        foreach (var table in tables)
        {
            var sortedCells = OrganizeCellsByCoordinates(table.CellInfos);

            Console.WriteLine("Organized Table Cells:");

            // int previousY = sortedCells.FirstOrDefault()?.CellRect.Y ?? 0;
            int previousY = sortedCells.Any() ? sortedCells.First().CellRect.Y : 0;

            foreach (var cell in sortedCells)
            {
                // Print a new line if the Y-coordinate changes, indicating a new row
                if (Math.Abs(cell.CellRect.Y - previousY) > cell.CellRect.Height * 0.8)
                {
                    Console.WriteLine();  // Start a new row
                    previousY = cell.CellRect.Y;
                }

                Console.Write($"{cell.CellText}\t");
            }

            Console.WriteLine("\n--- End of Table ---");
        }
    }

    public static List<CellInfo> ExtractRowByIndex(TableInfo table, int rowIndex)
    {
        if (table == null || table.CellInfos == null || !table.CellInfos.Any())
        {
            throw new ArgumentException("Table is empty or invalid.");
        }

        var sortedCells = OrganizeCellsByCoordinates(table.CellInfos);
        List<List<CellInfo>> rows = new List<List<CellInfo>>();

        // Group cells into rows
        int previousY = sortedCells.First().CellRect.Y;
        List<CellInfo> currentRow = new List<CellInfo>();

        foreach (var cell in sortedCells)
        {
            if (Math.Abs(cell.CellRect.Y - previousY) > cell.CellRect.Height * 0.8)
            {
                // Store the completed row and start a new one
                rows.Add(new List<CellInfo>(currentRow));
                currentRow.Clear();

                previousY = cell.CellRect.Y;
            }

            currentRow.Add(cell);
        }

        // Add the last row
        if (currentRow.Any())
        {
            rows.Add(currentRow);
        }

        // Retrieve the specific row
        if (rowIndex < 0 || rowIndex >= rows.Count)
        {
            throw new IndexOutOfRangeException($"Row index {rowIndex} is out of range.");
        }

        return rows[rowIndex];
    }
}
public static class TableProcessor
{
    public static List<CellInfo> OrganizeCellsByCoordinates(List<CellInfo> cells)
    {
        // Sort cells by Y (top to bottom), then by X (left to right)
        var sortedCells = cells
            .OrderBy(cell => cell.CellRect.Y)
            .ThenBy(cell => cell.CellRect.X)
            .ToList();

        return sortedCells;
    }

    // Example of how to use the function
    public static void ProcessTables(Tables tables)
    {
        foreach (var table in tables)
        {
            var sortedCells = OrganizeCellsByCoordinates(table.CellInfos);

            Console.WriteLine("Organized Table Cells:");

            // int previousY = sortedCells.FirstOrDefault()?.CellRect.Y ?? 0;
            int previousY = sortedCells.Any() ? sortedCells.First().CellRect.Y : 0;

            foreach (var cell in sortedCells)
            {
                // Print a new line if the Y-coordinate changes, indicating a new row
                if (Math.Abs(cell.CellRect.Y - previousY) > cell.CellRect.Height * 0.8)
                {
                    Console.WriteLine();  // Start a new row
                    previousY = cell.CellRect.Y;
                }

                Console.Write($"{cell.CellText}\t");
            }

            Console.WriteLine("\n--- End of Table ---");
        }
    }

    public static List<CellInfo> ExtractRowByIndex(TableInfo table, int rowIndex)
    {
        if (table == null || table.CellInfos == null || !table.CellInfos.Any())
        {
            throw new ArgumentException("Table is empty or invalid.");
        }

        var sortedCells = OrganizeCellsByCoordinates(table.CellInfos);
        List<List<CellInfo>> rows = new List<List<CellInfo>>();

        // Group cells into rows
        int previousY = sortedCells.First().CellRect.Y;
        List<CellInfo> currentRow = new List<CellInfo>();

        foreach (var cell in sortedCells)
        {
            if (Math.Abs(cell.CellRect.Y - previousY) > cell.CellRect.Height * 0.8)
            {
                // Store the completed row and start a new one
                rows.Add(new List<CellInfo>(currentRow));
                currentRow.Clear();

                previousY = cell.CellRect.Y;
            }

            currentRow.Add(cell);
        }

        // Add the last row
        if (currentRow.Any())
        {
            rows.Add(currentRow);
        }

        // Retrieve the specific row
        if (rowIndex < 0 || rowIndex >= rows.Count)
        {
            throw new IndexOutOfRangeException($"Row index {rowIndex} is out of range.");
        }

        return rows[rowIndex];
    }
}
Imports Microsoft.VisualBasic

Public Module TableProcessor
	Public Function OrganizeCellsByCoordinates(ByVal cells As List(Of CellInfo)) As List(Of CellInfo)
		' Sort cells by Y (top to bottom), then by X (left to right)
		Dim sortedCells = cells.OrderBy(Function(cell) cell.CellRect.Y).ThenBy(Function(cell) cell.CellRect.X).ToList()

		Return sortedCells
	End Function

	' Example of how to use the function
	Public Sub ProcessTables(ByVal tables As Tables)
		For Each table In tables
			Dim sortedCells = OrganizeCellsByCoordinates(table.CellInfos)

			Console.WriteLine("Organized Table Cells:")

			' int previousY = sortedCells.FirstOrDefault()?.CellRect.Y ?? 0;
			Dim previousY As Integer = If(sortedCells.Any(), sortedCells.First().CellRect.Y, 0)

			For Each cell In sortedCells
				' Print a new line if the Y-coordinate changes, indicating a new row
				If Math.Abs(cell.CellRect.Y - previousY) > cell.CellRect.Height * 0.8 Then
					Console.WriteLine() ' Start a new row
					previousY = cell.CellRect.Y
				End If

				Console.Write($"{cell.CellText}" & vbTab)
			Next cell

			Console.WriteLine(vbLf & "--- End of Table ---")
		Next table
	End Sub

	Public Function ExtractRowByIndex(ByVal table As TableInfo, ByVal rowIndex As Integer) As List(Of CellInfo)
		If table Is Nothing OrElse table.CellInfos Is Nothing OrElse Not table.CellInfos.Any() Then
			Throw New ArgumentException("Table is empty or invalid.")
		End If

		Dim sortedCells = OrganizeCellsByCoordinates(table.CellInfos)
		Dim rows As New List(Of List(Of CellInfo))()

		' Group cells into rows
		Dim previousY As Integer = sortedCells.First().CellRect.Y
		Dim currentRow As New List(Of CellInfo)()

		For Each cell In sortedCells
			If Math.Abs(cell.CellRect.Y - previousY) > cell.CellRect.Height * 0.8 Then
				' Store the completed row and start a new one
				rows.Add(New List(Of CellInfo)(currentRow))
				currentRow.Clear()

				previousY = cell.CellRect.Y
			End If

			currentRow.Add(cell)
		Next cell

		' Add the last row
		If currentRow.Any() Then
			rows.Add(currentRow)
		End If

		' Retrieve the specific row
		If rowIndex < 0 OrElse rowIndex >= rows.Count Then
			Throw New IndexOutOfRangeException($"Row index {rowIndex} is out of range.")
		End If

		Return rows(rowIndex)
	End Function
End Module
VB   C#