从PDF中提取标记内容

在本文中，您将学习如何使用C#提取标记内容的PDF文档。

以下代码片段也适用于Aspose.PDF.Drawing库。

获取标记PDF内容

为了获取带有标记文本的PDF文档内容，Aspose.PDF提供了Document类的TaggedContent属性。

以下代码片段演示了如何获取带有标记文本的PDF文档内容：

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void GetTaggedContent()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_WorkingDocuments();

    // Create PDF Document
    using (var document = new Aspose.Pdf.Document())
    {
        // Get Content for work with Tagged PDF
        Aspose.Pdf.Tagged.ITaggedContent taggedContent = document.TaggedContent;

        // Work with Tagged PDF content
        // Set Title and Language for Document
        taggedContent.SetTitle("Simple Tagged Pdf Document");
        taggedContent.SetLanguage("en-US");

        // Save Tagged PDF Document
        document.Save(dataDir + "TaggedPDFContent_out.pdf");
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void GetTaggedContent()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_WorkingDocuments();

    // Create PDF Document
    using var document = new Aspose.Pdf.Document();

    // Get Content for work with TaggedPdf
    Aspose.Pdf.Tagged.ITaggedContent taggedContent = document.TaggedContent;

    // Work with Tagged PDF content
    // Set Title and Language for Document
    taggedContent.SetTitle("Simple Tagged Pdf Document");
    taggedContent.SetLanguage("en-US");

    // Save Tagged PDF Document
    document.Save(dataDir + "TaggedPDFContent_out.pdf");
}

获取根结构

为了获取标记PDF文档的根结构，Aspose.PDF提供了ITaggedContent接口的StructTreeRootElement属性和StructureElement。以下代码片段演示了如何获取标记PDF文档的根结构：

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void GetRootStructure()
{
    // Create PDF Document
    using (var document = new Aspose.Pdf.Document())
    {
        // Get Content for work with Tagged PDF
        Aspose.Pdf.Tagged.ITaggedContent taggedContent = document.TaggedContent;

        // Set Title and Language for Document
        taggedContent.SetTitle("Tagged Pdf Document");
        taggedContent.SetLanguage("en-US");

        // Properties StructTreeRootElement and RootElement are used for access to
        // StructTreeRoot object of pdf document and to root structure element (Document structure element).
        Aspose.Pdf.LogicalStructure.StructTreeRootElement structTreeRootElement = taggedContent.StructTreeRootElement;
        Aspose.Pdf.LogicalStructure.StructureElement rootElement = taggedContent.RootElement;
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void GetRootStructure()
{
    // Create PDF Document
    using var document = new Aspose.Pdf.Document();

    // Get Content for work with Tagged PDF
    Aspose.Pdf.Tagged.ITaggedContent taggedContent = document.TaggedContent;

    // Set Title and Language for Document
    taggedContent.SetTitle("Tagged Pdf Document");
    taggedContent.SetLanguage("en-US");

    // Properties StructTreeRootElement and RootElement are used for access to
    // StructTreeRoot object of pdf document and to root structure element (Document structure element).
    Aspose.Pdf.LogicalStructure.StructTreeRootElement structTreeRootElement = taggedContent.StructTreeRootElement;
    Aspose.Pdf.LogicalStructure.StructureElement rootElement = taggedContent.RootElement;
}

访问子元素

为了访问标记PDF文档的子元素，Aspose.PDF提供了ElementList类。以下代码片段演示了如何访问标记PDF文档的子元素：

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void AccessChildElements()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_WorkingDocuments();

    // Open PDF Document
    using (var document = new Aspose.Pdf.Document(dataDir + "StructureElementsTree.pdf"))
    {
        // Get Content for work with Tagged PDF
        Aspose.Pdf.Tagged.ITaggedContent taggedContent = document.TaggedContent;

        // Access to root element(s)
        Aspose.Pdf.LogicalStructure.ElementList elementList = taggedContent.StructTreeRootElement.ChildElements;

        foreach (Aspose.Pdf.LogicalStructure.Element element in elementList)
        {
            if (element is Aspose.Pdf.LogicalStructure.StructureElement)
            {
                var structureElement = element as Aspose.Pdf.LogicalStructure.StructureElement;

                // Get properties
                string title = structureElement.Title;
                string language = structureElement.Language;
                string actualText = structureElement.ActualText;
                string expansionText = structureElement.ExpansionText;
                string alternativeText = structureElement.AlternativeText;
            }
        }

        // Access to child elements of first element in root element
        elementList = taggedContent.RootElement.ChildElements[1].ChildElements;

        foreach (Aspose.Pdf.LogicalStructure.Element element in elementList)
        {
            if (element is Aspose.Pdf.LogicalStructure.StructureElement)
            {
                var structureElement = element as Aspose.Pdf.LogicalStructure.StructureElement;

                // Set properties
                structureElement.Title = "title";
                structureElement.Language = "fr-FR";
                structureElement.ActualText = "actual text";
                structureElement.ExpansionText = "exp";
                structureElement.AlternativeText = "alt";
            }
        }

        // Save Tagged PDF Document
        document.Save(dataDir + "AccessChildElements_out.pdf");
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void AccessChildElements()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_WorkingDocuments();

    // Open PDF Document
    using var document = new Aspose.Pdf.Document(dataDir + "StructureElementsTree.pdf");

    // Get Content for work with Tagged PDF
    Aspose.Pdf.Tagged.ITaggedContent taggedContent = document.TaggedContent;

    // Access to root element(s)
    Aspose.Pdf.LogicalStructure.ElementList elementList = taggedContent.StructTreeRootElement.ChildElements;

    foreach (Aspose.Pdf.LogicalStructure.Element element in elementList)
    {
        if (element is Aspose.Pdf.LogicalStructure.StructureElement)
        {
            var structureElement = element as Aspose.Pdf.LogicalStructure.StructureElement;

            // Get properties
            string title = structureElement.Title;
            string language = structureElement.Language;
            string actualText = structureElement.ActualText;
            string expansionText = structureElement.ExpansionText;
            string alternativeText = structureElement.AlternativeText;
        }
    }

    // Access to child elements of first element in root element
    elementList = taggedContent.RootElement.ChildElements[1].ChildElements;

    foreach (Aspose.Pdf.LogicalStructure.Element element in elementList)
    {
        if (element is Aspose.Pdf.LogicalStructure.StructureElement)
        {
            var structureElement = element as Aspose.Pdf.LogicalStructure.StructureElement;

            // Set properties
            structureElement.Title = "title";
            structureElement.Language = "fr-FR";
            structureElement.ActualText = "actual text";
            structureElement.ExpansionText = "exp";
            structureElement.AlternativeText = "alt";
        }
    }

    // Save Tagged PDF Document
    document.Save(dataDir + "AccessChildElements_out.pdf");
}

在现有PDF中标记图像

为了在现有PDF文档中标记图像，Aspose.PDF提供了StructureElement类的FindElements方法。您可以使用FigureElement类的AlternativeText属性为图形添加替代文本。

以下代码片段演示了如何在现有PDF文档中标记图像：

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void TagImages()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_WorkingDocuments();

    // Open PDF document
    using (var document1 = new Aspose.Pdf.Document(dataDir + "TH.pdf"))
    {
        // Gets tagged content and root structure element
        Aspose.Pdf.Tagged.ITaggedContent taggedContent = document1.TaggedContent;
        Aspose.Pdf.LogicalStructure.StructureElement rootElement = taggedContent.RootElement;

        // Set title for tagged PDF document
        taggedContent.SetTitle("Document with images");

        foreach (Aspose.Pdf.LogicalStructure.FigureElement figureElement in rootElement.FindElements<Aspose.Pdf.LogicalStructure.FigureElement>(true))
        {
            // Set AlternativeText for Figure
            figureElement.AlternativeText = "Figure alternative text (technique 2)";

            // Create and Set BBox Attribute
            var bboxAttribute = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.BBox);
            bboxAttribute.SetRectangleValue(new Aspose.Pdf.Rectangle(0.0, 0.0, 100.0, 100.0));

            Aspose.Pdf.LogicalStructure.StructureAttributes figureLayoutAttributes = figureElement.Attributes.GetAttributes(Aspose.Pdf.LogicalStructure.AttributeOwnerStandard.Layout);
            figureLayoutAttributes.SetAttribute(bboxAttribute);
        }

        // Move Span Element into Paragraph (find wrong span and paragraph in first TD)
        Aspose.Pdf.LogicalStructure.TableElement tableElement = rootElement.FindElements<Aspose.Pdf.LogicalStructure.TableElement>(true)[0];
        Aspose.Pdf.LogicalStructure.SpanElement spanElement = tableElement.FindElements<Aspose.Pdf.LogicalStructure.SpanElement>(true)[0];
        Aspose.Pdf.LogicalStructure.TableTDElement firstTdElement = tableElement.FindElements<Aspose.Pdf.LogicalStructure.TableTDElement>(true)[0];
        Aspose.Pdf.LogicalStructure.ParagraphElement paragraph = firstTdElement.FindElements<Aspose.Pdf.LogicalStructure.ParagraphElement>(true)[0];

        // Move Span Element into Paragraph
        spanElement.ChangeParentElement(paragraph);

        // Save PDF document
        document1.Save(dataDir + "TH_out.pdf");
    }

    // Check PDF/UA Compliance for out document
    using (var document2 = new Aspose.Pdf.Document(dataDir + "TH_out.pdf"))
    {
        bool isPdfUaCompliance = document2.Validate(dataDir + "TH_out.xml", Aspose.Pdf.PdfFormat.PDF_UA_1);
        Console.WriteLine(String.Format("PDF/UA compliance: {0}", isPdfUaCompliance));
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void TagImages()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_WorkingDocuments();

    // Open PDF document
    using var document1 = new Aspose.Pdf.Document(dataDir + "TH.pdf");

    // Gets tagged content and root structure element
    Aspose.Pdf.Tagged.ITaggedContent taggedContent = document1.TaggedContent;
    Aspose.Pdf.LogicalStructure.StructureElement rootElement = taggedContent.RootElement;

    // Set title for tagged PDF document
    taggedContent.SetTitle("Document with images");

    foreach (Aspose.Pdf.LogicalStructure.FigureElement figureElement in rootElement.FindElements<Aspose.Pdf.LogicalStructure.FigureElement>(true))
    {
        // Set AlternativeText for Figure
        figureElement.AlternativeText = "Figure alternative text (technique 2)";

        // Create and Set BBox Attribute
        var bboxAttribute = new Aspose.Pdf.LogicalStructure.StructureAttribute(Aspose.Pdf.LogicalStructure.AttributeKey.BBox);
        bboxAttribute.SetRectangleValue(new Aspose.Pdf.Rectangle(0.0, 0.0, 100.0, 100.0));

        Aspose.Pdf.LogicalStructure.StructureAttributes figureLayoutAttributes = figureElement.Attributes.GetAttributes(Aspose.Pdf.LogicalStructure.AttributeOwnerStandard.Layout);
        figureLayoutAttributes.SetAttribute(bboxAttribute);
    }

    // Move Span Element into Paragraph (find wrong span and paragraph in first TD)
    Aspose.Pdf.LogicalStructure.TableElement tableElement = rootElement.FindElements<Aspose.Pdf.LogicalStructure.TableElement>(true)[0];
    Aspose.Pdf.LogicalStructure.SpanElement spanElement = tableElement.FindElements<Aspose.Pdf.LogicalStructure.SpanElement>(true)[0];
    Aspose.Pdf.LogicalStructure.TableTDElement firstTdElement = tableElement.FindElements<Aspose.Pdf.LogicalStructure.TableTDElement>(true)[0];
    Aspose.Pdf.LogicalStructure.ParagraphElement paragraph = firstTdElement.FindElements<Aspose.Pdf.LogicalStructure.ParagraphElement>(true)[0];

    // Move Span Element into Paragraph
    spanElement.ChangeParentElement(paragraph);

    // Save PDF document
    document1.Save(dataDir + "TH_out.pdf");

    // Check PDF/UA Compliance for out document
    using var document2 = new Aspose.Pdf.Document(dataDir + "TH_out.pdf");

    bool isPdfUaCompliance = document2.Validate(dataDir + "TH_out.pdf", Aspose.Pdf.PdfFormat.PDF_UA_1);
    Console.WriteLine(String.Format("PDF/UA compliance: {0}", isPdfUaCompliance));
}