C# 如何使用PDFBox阅读PDF部门（标题、摘要、参考资料）？

我试图阅读PDF文件及其部门，但我找不到正确的算法或库

我想分离文件的各个部分（标题、摘要、引用）并返回它们的内容

---

是否存在解决此问题的参考？

遗憾的是，OP作为代表性示例提供的文件没有标记。因此，没有直接的信息表明给定的文本是否属于标题、摘要、参考文献或任何部分。因此，没有确定的方法来识别这些部分，而仅仅是启发式，即受过教育的猜测，或多或少有很大的错误率

对于OP提供的样本文档，零件的识别实际上可以通过简单检查每行第一个字母的字体来完成

下面的类构成了一个简单的框架，用于提取语义文本部分，这些部分仅通过每行的特征就可以识别，并通过仅检查每行第一个字符的字体来识别OP示例文件中的部分

简单文本节提取框架 由于我只使用过PDFBox的Java版本，OP声明Java解决方案也可以，所以该框架是用Java实现的。它基于PDFBox的当前开发版本2.1.0-SNAPSHOT

PDFTextSectionStripper

此类构成了框架的中心。它派生自PDFBox

PdfTextStripper

，并通过识别由

TextSectionDefinition

实例列表配置的文本节来扩展该类，如下所示。调用

PdfTextStripper

方法

getText

后，识别的部分将作为

textcreation

实例列表提供，请参见下文

public class PDFTextSectionStripper extends PDFTextStripper
{
    //
    // constructor
    //
    public PDFTextSectionStripper(List<TextSectionDefinition> sectionDefinitions) throws IOException
    {
        super();
        
        this.sectionDefinitions = sectionDefinitions;
    }

    //
    // Section retrieval
    //
    /**
     * @return an unmodifiable list of text sections recognized during {@link #getText(PDDocument)}.
     */
    public List<TextSection> getSections()
    {
        return Collections.unmodifiableList(sections);
    }

    //
    // PDFTextStripper overrides
    //
    @Override
    protected void writeLineSeparator() throws IOException
    {
        super.writeLineSeparator();

        if (!currentLine.isEmpty())
        {
            boolean matched = false;
            if (!(currentHeader.isEmpty() && currentBody.isEmpty()))
            {
                TextSectionDefinition definition = sectionDefinitions.get(currentSectionDefinition);
                switch (definition.multiLine)
                {
                case multiLine:
                    if (definition.matchPredicate.test(currentLine))
                    {
                        currentBody.add(new ArrayList<>(currentLine));
                        matched = true;
                    }
                    break;
                case multiLineHeader:
                case multiLineIntro:
                    boolean followUpMatch = false;
                    for (int i = definition.multiple ? currentSectionDefinition : currentSectionDefinition + 1;
                            i < sectionDefinitions.size(); i++)
                    {
                        TextSectionDefinition followUpDefinition = sectionDefinitions.get(i);
                        if (followUpDefinition.matchPredicate.test(currentLine))
                        {
                            followUpMatch = true;
                            break;
                        }
                    }
                    if (!followUpMatch)
                    {
                        currentBody.add(new ArrayList<>(currentLine));
                        matched = true;
                    }
                    break;
                case singleLine:
                    System.out.println("Internal error: There can be no current header or body as long as the current definition is single line only");
                }

                if (!matched)
                {
                    sections.add(new TextSection(definition, currentHeader, currentBody));
                    currentHeader.clear();
                    currentBody.clear();
                    if (!definition.multiple)
                        currentSectionDefinition++;
                }
            }

            if (!matched)
            {
                while (currentSectionDefinition < sectionDefinitions.size())
                {
                    TextSectionDefinition definition = sectionDefinitions.get(currentSectionDefinition);
                    if (definition.matchPredicate.test(currentLine))
                    {
                        matched = true;
                        switch (definition.multiLine)
                        {
                        case singleLine:
                            sections.add(new TextSection(definition, currentLine, Collections.emptyList()));
                            if (!definition.multiple)
                                currentSectionDefinition++;
                            break;
                        case multiLineHeader:
                            currentHeader.addAll(new ArrayList<>(currentLine));
                            break;
                        case multiLine:
                        case multiLineIntro:
                            currentBody.add(new ArrayList<>(currentLine));
                            break;
                        }
                        break;
                    }

                    currentSectionDefinition++;
                }
            }

            if (!matched)
            {
                System.out.println("Could not match line.");
            }
        }
        currentLine.clear();
    }

    @Override
    protected void endDocument(PDDocument document) throws IOException
    {
        super.endDocument(document);

        if (!(currentHeader.isEmpty() && currentBody.isEmpty()))
        {
            TextSectionDefinition definition = sectionDefinitions.get(currentSectionDefinition);
            sections.add(new TextSection(definition, currentHeader, currentBody));
            currentHeader.clear();
            currentBody.clear();
        }
    }

    @Override
    protected void writeString(String text, List<TextPosition> textPositions) throws IOException
    {
        super.writeString(text, textPositions);

        currentLine.add(textPositions);
    }
    
    //
    // member variables
    //
    final List<TextSectionDefinition> sectionDefinitions;

    int currentSectionDefinition = 0;
    final List<TextSection> sections = new ArrayList<>();
    final List<List<TextPosition>> currentLine = new ArrayList<>();

    final List<List<TextPosition>> currentHeader = new ArrayList<>();
    final List<List<List<TextPosition>>> currentBody = new ArrayList<>();
}

（）

TextSection

此类表示此框架识别的文本部分

public class TextSection
{
    public TextSection(TextSectionDefinition definition, List<List<TextPosition>> header, List<List<List<TextPosition>>> body)
    {
        this.definition = definition;
        this.header = new ArrayList<>(header);
        this.body = new ArrayList<>(body);
    }

    @Override
    public String toString()
    {
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append(definition.name).append(": ");
        if (!header.isEmpty())
            stringBuilder.append(toString(header));
        stringBuilder.append('\n');
        for (List<List<TextPosition>> bodyLine : body)
        {
            stringBuilder.append("    ").append(toString(bodyLine)).append('\n');
        }
        return stringBuilder.toString();
    }

    String toString(List<List<TextPosition>> words)
    {
        StringBuilder stringBuilder = new StringBuilder();
        boolean first = true;
        for (List<TextPosition> word : words)
        {
            if (first)
                first = false;
            else
                stringBuilder.append(' ');
            for (TextPosition textPosition : word)
            {
                stringBuilder.append(textPosition.getUnicode());
            }
        }
        // cf. https://stackoverflow.com/a/7171932/1729265
        return Normalizer.normalize(stringBuilder, Form.NFKC);
    }

    final TextSectionDefinition definition;
    final List<List<TextPosition>> header;
    final List<List<List<TextPosition>>> body;
}

（试验方法

testWang05a

）

结果是：

Titel: How to Break MD5 and Other Hash Functions

Authors: 
    Xiaoyun Wang and Hongbo Yu

Institutions: 
    Shandong University, Jinan 250100, China,

Addresses: 
    xywang@sdu.edu.cn, yhb@mail.sdu.edu.cn

Abstract: 
    Abstract. MD5 is one of the most widely used cryptographic hash func-
    tions nowadays. It was designed in 1992 as an improvement of MD4, and
    ...

Section: 1 Introduction
    People know that digital signatures are very important in information security.
    The security of digital signatures depends on the cryptographic strength of the
    ...

Section: 2 Description of MD5
    In order to conveniently describe the general structure of MD5, we first recall
    the iteration process for hash functions.
    ...

Section: 3 Differential Attack for Hash Functions
    3.1 The Modular Differential and the XOR Differential
    The most important analysis method for hash functions is differential attack
    ...

Section: 4 Differential Attack on MD5
    4.1 Notation
    Before presenting our attack, we first introduce some notation to simplify the
    ...

Section: 5 Summary
    In this paper we described a powerful attack against hash functions, and in
    particular showed that finding a collision of MD5 is easily feasible.
    ...

Section: Acknowledgements
    It is a pleasure to acknowledge Dengguo Feng for the conversations that led to
    this research on MD5. We would like to thank Eli Biham, Andrew C. Yao, and
    ...

Section: References
    1. E. Biham, A. Shamir. Differential Cryptanalysis of the Data Encryption Standard,
    Springer-Verlag, 1993.
    ...

---

对于更通用的文本部分识别，显然不能指望使用这些特定的TeX字体来表示特定的文本部分。相反，您可能需要查看字体大小（记住不要使用简单的字体大小属性，而是根据转换和文本矩阵进行缩放！）、对齐方式等。可能需要首先扫描文档以确定常见的文本大小等

---

但是，对于同一杂志中发布的多个文档，识别谓词实际上可能与上面的示例一样简单，因为在这种情况下，作者通常必须遵守非常具体的布局和格式规则。

如果您指的是提取表，则PDFBox无法做到这一点，除非您确切知道所有内容的位置。也许tabla可以帮你，这是在PDFBox上面。你想要哪种PDF？我问，因为任务变得更困难，你必须考虑的PDF集越大。@ MKL，我用PDFox读取PEPEX和管理PEAPEX扫描库，共享一组有代表性的PDF来分析模式来识别所搜索的部分。

List<TextSectionDefinition> sectionDefinitions = Arrays.asList(
        new TextSectionDefinition("Titel", x->x.get(0).get(0).getFont().getName().contains("CMBX12"), MultiLine.singleLine, false),
        new TextSectionDefinition("Authors", x->x.get(0).get(0).getFont().getName().contains("CMR10"), MultiLine.multiLine, false),
        new TextSectionDefinition("Institutions", x->x.get(0).get(0).getFont().getName().contains("CMR9"), MultiLine.multiLine, false),
        new TextSectionDefinition("Addresses", x->x.get(0).get(0).getFont().getName().contains("CMTT9"), MultiLine.multiLine, false),
        new TextSectionDefinition("Abstract", x->x.get(0).get(0).getFont().getName().contains("CMBX9"), MultiLine.multiLineIntro, false),
        new TextSectionDefinition("Section", x->x.get(0).get(0).getFont().getName().contains("CMBX12"), MultiLine.multiLineHeader, true)
        );

PDDocument document = PDDocument.load(resource);
PDFTextSectionStripper stripper = new PDFTextSectionStripper(sectionDefinitions);
stripper.getText(document);

System.out.println("Sections:");
List<String> texts = new ArrayList<>();
for (TextSection textSection : stripper.getSections())
{
    String text = textSection.toString();
    System.out.println(text);
    texts.add(text);
}
Files.write(new File(RESULT_FOLDER, "Wang05a.txt").toPath(), texts);

Titel: How to Break MD5 and Other Hash Functions

Authors: 
    Xiaoyun Wang and Hongbo Yu

Institutions: 
    Shandong University, Jinan 250100, China,

Addresses: 
    xywang@sdu.edu.cn, yhb@mail.sdu.edu.cn

Abstract: 
    Abstract. MD5 is one of the most widely used cryptographic hash func-
    tions nowadays. It was designed in 1992 as an improvement of MD4, and
    ...

Section: 1 Introduction
    People know that digital signatures are very important in information security.
    The security of digital signatures depends on the cryptographic strength of the
    ...

Section: 2 Description of MD5
    In order to conveniently describe the general structure of MD5, we first recall
    the iteration process for hash functions.
    ...

Section: 3 Differential Attack for Hash Functions
    3.1 The Modular Differential and the XOR Differential
    The most important analysis method for hash functions is differential attack
    ...

Section: 4 Differential Attack on MD5
    4.1 Notation
    Before presenting our attack, we first introduce some notation to simplify the
    ...

Section: 5 Summary
    In this paper we described a powerful attack against hash functions, and in
    particular showed that finding a collision of MD5 is easily feasible.
    ...

Section: Acknowledgements
    It is a pleasure to acknowledge Dengguo Feng for the conversations that led to
    this research on MD5. We would like to thank Eli Biham, Andrew C. Yao, and
    ...

Section: References
    1. E. Biham, A. Shamir. Differential Cryptanalysis of the Data Encryption Standard,
    Springer-Verlag, 1993.
    ...