用Csharp调用itext读取pdf文件，并提取出文本，相邻文本距离超过一个字宽度的用空格补齐。

以下是使用C#调用itext读取pdf文件并提取文本的示例代码：

using iText.Kernel.Pdf;
using iText.Kernel.Pdf.Canvas.Parser;
using iText.Kernel.Pdf.Canvas.Parser.Listener;
using System.Text;

public static string ExtractTextFromPDF(string filepath)
{
    StringBuilder sb = new StringBuilder();

    using (PdfReader reader = new PdfReader(filepath))
    {
        using (PdfDocument pdfDoc = new PdfDocument(reader))
        {
            for (int i = 1; i <= pdfDoc.GetNumberOfPages(); i++)
            {
                PdfPage page = pdfDoc.GetPage(i);
                ITextExtractionStrategy strategy = new SimpleTextExtractionStrategy();
                string text = PdfTextExtractor.GetTextFromPage(page, strategy);
                sb.Append(text);
            }
        }
    }

    return sb.ToString();
}

为了实现相邻文本距离超过一个字宽度的用空格补齐的功能，我们可以在获取文本时添加一些额外的处理：

public static string ExtractTextFromPDF(string filepath)
{
    StringBuilder sb = new StringBuilder();

    using (PdfReader reader = new PdfReader(filepath))
    {
        using (PdfDocument pdfDoc = new PdfDocument(reader))
        {
            for (int i = 1; i <= pdfDoc.GetNumberOfPages(); i++)
            {
                PdfPage page = pdfDoc.GetPage(i);
                CustomTextExtractionStrategy strategy = new CustomTextExtractionStrategy();
                string text = PdfTextExtractor.GetTextFromPage(page, strategy);

                // 将相邻文本距离超过一个字宽度的用空格补齐
                text = strategy.FillInSpaceBetweenWords(text);

                sb.Append(text);
            }
        }
    }

    return sb.ToString();
}

public class CustomTextExtractionStrategy : LocationTextExtractionStrategy
{
    // 记录当前字符的左上角坐标
    private Vector lastStart;

    public override void BeginTextBlock()
    {
        base.BeginTextBlock();
        lastStart = null;
    }

    public override void RenderText(TextRenderInfo renderInfo)
    {
        base.RenderText(renderInfo);

        Vector start = renderInfo.GetDescentLine().GetStartPoint();
        Vector end = renderInfo.GetAscentLine().GetEndPoint();

        if (lastStart != null)
        {
            // 计算当前字符的左上角坐标和上一个字符的右上角坐标之间的距离
            float distance = start.Subtract(lastStart).Length();

            // 如果距离大于一个字宽度，则认为中间需要插入一个空格
            if (distance > renderInfo.GetSingleSpaceWidth())
            {
                AppendText(" ");
            }
        }

        AppendText(renderInfo.GetText());
        lastStart = start;
    }

    // 将相邻文本距离超过一个字宽度的用空格补齐
    public string FillInSpaceBetweenWords(string text)
    {
        StringBuilder sb = new StringBuilder();
        char[] chars = text.ToCharArray();

        for (int i = 0; i < chars.Length; i++)
        {
            sb.Append(chars[i]);

            if (i < chars.Length - 1)
            {
                // 计算当前字符和下一个字符的距离
                float distance = GetDistanceBetweenChars(chars[i], chars[i + 1]);

                // 如果距离大于一个字宽度，则认为中间需要插入一个空格
                if (distance > GetSingleSpaceWidth())
                {
                    sb.Append(" ");
                }
            }
        }

        return sb.ToString();
    }

    // 获取两个字符之间的距离
    private float GetDistanceBetweenChars(char c1, char c2)
    {
        Glyph glyph1 = font.GetGlyph(c1);
        Glyph glyph2 = font.GetGlyph(c2);
        return glyph1.GetWidth() + glyph2.GetWidth() - glyph1.GetBoundingBox().GetRight();
    }

    // 获取一个空格的宽度
    public float GetSingleSpaceWidth()
    {
        Glyph glyph = font.GetGlyph(' ');
        return glyph.GetWidth();
    }
}