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借助 TX Text Control：在 .NET C# 中验证 PDF/UA 文档

news 2026/6/11 19:35:32

创建易于访问且符合规范的 PDF 文档正成为各行各业日益重要的需求。在本篇博文中，我们将探讨如何使用 Text Control 的 .NET 库验证 PDF/UA 文档，轻松确保生成的 PDF 符合无障碍标准。TX Text Control 34.0 将允许开发人员直接生成 PDF/UA 和 PDF/A-3a 文档，这对于长期、合规的文档归档而言是一项重大进步。

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什么是 PDF/UA 和 PDF/A-3a？

PDF/UA（通用无障碍）制定了确保所有人都能访问 PDF 文档的标准，包括使用辅助技术（如屏幕阅读器）的用户。

PDF/UA 确保文档的结构、阅读顺序和元素描述得到正确定义，以便所有内容都能在语义上被理解。

另一方面，PDF/A-3a 是 ISO 标准化的归档 PDF 格式系列的一部分。它保证文档可以原封不动地复制，包括嵌入式附件和可访问内容（“a”代表“可访问性”）。

这两个标准都要求文档包含逻辑结构、语义标签和准确描述内容的元数据。

为什么验证至关重要

在生成 PDF/UA 文件或设计模板的过程中，一些标签或描述性元素经常会丢失或应用错误。即使文档在视觉上看起来没有问题，但它可能不符合无障碍或存档标准，因此无法通过合规性检查。

例如：

某个图表可能缺少描述性文字。
表格可能缺少正确的表头定义。
阅读顺序或标签层级结构可能被打乱了。
可能未设置语言或文档标题等元数据。

如果没有验证，这些问题很容易被忽视。

PDF/UA验证

在 34.0 版本中，我们将引入一个验证库，旨在帮助开发人员检查生成的 PDF 文档的合规性。

该库分析：

文档结构树和标签层次结构
元数据和语言设置
表格、图表、表单字段和超链接的描述性文本
表头和数据单元格的关系
以及 PDF/UA 规范要求的其他与辅助功能相关的属性

它以结构化的 JSON 格式生成详细报告，并为控制台应用程序提供文本输出。这使得开发人员能够将验证直接集成到自动化测试或质量保证 (QA) 流程中。

C# 中的示例用法

以下是一个如何在 C# 应用程序中使用验证库的简单示例：

using TXTextControl.PDF.Validation;var report = PdfUaValidator.Validate("documents/hyperlink.pdf");
report.PrintText();

在这个例子中，我们首先创建一个验证器实例，然后验证文档。验证结果会输出到控制台，并可以序列化为 JSON 格式以进行进一步分析。

生成的 JSON 报告详细概述了文档中发现的所有合规性问题：

{"filePath": "documents/hyperlink.pdf","pdfVersion": "1.7","isPass": true,"documentTitle": "This is a sample PDF/UA document","documentLanguage": "en-US","findings": [{"ruleId": "UA-CONFORMANCE","severity": "Info","passed": true,"message": "PDF/UA-1 conformance declaration found in XMP."},{"ruleId": "PDFA-CONFORMANCE","severity": "Info","passed": true,"message": "PDF/A-3A declaration found in XMP."},{"ruleId": "PDF-HEADER","severity": "Error","passed": true,"message": "Found PDF header %PDF-1.7."},{"ruleId": "PDF-XREF","severity": "Warning","passed": true,"message": "Cross-reference table/stream appears present."},{"ruleId": "UA-CATALOG","severity": "Error","passed": true,"message": "Catalog dictionary present."},{"ruleId": "UA-MARKED","severity": "Error","passed": true,"message": "/MarkInfo \u003C\u003C /Marked true \u003E\u003E found (Tagged PDF)."},{"ruleId": "UA-STRUCT","severity": "Error","passed": true,"message": "/StructTreeRoot present."},{"ruleId": "UA-MCID-ANCHOR","severity": "Info","passed": true,"message": "Marked content (/MCID) present and at least one page has /StructParents anchors."},{"ruleId": "UA-TEXT-MAPPING","severity": "Info","passed": true,"message": "Font ToUnicode maps present (text is likely accessible)."},{"ruleId": "UA-LANG","severity": "Error","passed": true,"message": "/Lang present at document/page level."},{"ruleId": "UA-METADATA","severity": "Warning","passed": true,"message": "XMP metadata packet detected."},{"ruleId": "UA-TITLE","severity": "Error","passed": true,"message": "Document title found (Info or XMP dc:title)."},{"ruleId": "UA-TABS","severity": "Warning","passed": true,"message": "Page /Tabs setting present."},{"ruleId": "UA-FIG-ALT","severity": "Info","passed": true,"message": "Figures detected: 3; descriptive text tokens (/Alt or /ActualText): 3."},{"ruleId": "UA-LINK-DESC","severity": "Info","passed": true,"message": "Links: 2; all appear to have nearby tooltip/contents/ActualText."},{"ruleId": "UA-FORMS-TU","severity": "Info","passed": true,"message": "AcroForm detected; tooltips (/TU) count: 3."},{"ruleId": "UA-TABLE-A-SUMMARY","severity": "Info","passed": true,"message": "Tables: 3; all have /A with /Summary."},{"ruleId": "UA-TABLE-HEADERS","severity": "Info","passed": true,"message": "Tables with headers: OK=1, missing/invalid=0."}],"tableSummaries": [{"index": 1,"summaryText": "Table description","summaryRaw": "(\u00FE\u00FF\u0000T\u0000a\u0000b\u0000l\u0000e\u0000 \u0000d\u0000e\u0000s\u0000c\u0000r\u0000i\u0000p\u0000t\u0000i\u0000o\u0000n)","hasOTable": true,"source": "Obj 58: A 74 0 R","thTotal": 3,"thWithScope": 3,"tdWithHeaders": 0,"headersOk": true,"headersApplicable": true},{"index": 2,"summaryText": "Inner table","summaryRaw": "(\u00FE\u00FF\u0000I\u0000n\u0000n\u0000e\u0000r\u0000 \u0000t\u0000a\u0000b\u0000l\u0000e)","hasOTable": true,"source": "Obj 59: A 96 0 R","thTotal": 0,"thWithScope": 0,"tdWithHeaders": 0,"headersOk": true,"headersApplicable": false},{"index": 3,"summaryText": "Third table","summaryRaw": "(\u00FE\u00FF\u0000T\u0000h\u0000i\u0000r\u0000d\u0000 \u0000t\u0000a\u0000b\u0000l\u0000e)","hasOTable": true,"source": "Obj 60: A 122 0 R","thTotal": 0,"thWithScope": 0,"tdWithHeaders": 0,"headersOk": true,"headersApplicable": false}],"links": [{"index": 1,"linkText": "Descriptive Text","linkTextRaw": "(\u00FE\u00FF\u0000D\u0000e\u0000s\u0000c\u0000r\u0000i\u0000p\u0000t\u0000i\u0000v\u0000e\u0000 \u0000T\u0000e\u0000x\u0000t)","targetType": "URI","targetValue": "http://www.textcontrol.com","targetRaw": "(http://www.textcontrol.com)","source": "Annot window"},{"index": 2,"linkText": "Descriptive Text","linkTextRaw": "(\u00FE\u00FF\u0000D\u0000e\u0000s\u0000c\u0000r\u0000i\u0000p\u0000t\u0000i\u0000v\u0000e\u0000 \u0000T\u0000e\u0000x\u0000t)","targetType": "URI","targetValue": "http://www.textcontrol.com","targetRaw": "(http://www.textcontrol.com)","source": "Annot window"}],"figures": [{"index": 1,"altText": "image in  table","altRaw": "(\u00FE\u00FF\u0000i\u0000m\u0000a\u0000g\u0000e\u0000 \u0000i\u0000n\u0000 \u0000 \u0000t\u0000a\u0000b\u0000l\u0000e)","source": "Figure obj 55"},{"index": 2,"altText": "Barcode not in table","altRaw": "(\u00FE\u00FF\u0000B\u0000a\u0000r\u0000c\u0000o\u0000d\u0000e\u0000 \u0000n\u0000o\u0000t\u0000 \u0000i\u0000n\u0000 \u0000t\u0000a\u0000b\u0000l\u0000e)","source": "Figure obj 56"},{"index": 3,"altText": "Image description","altRaw": "(\u00FE\u00FF\u0000I\u0000m\u0000a\u0000g\u0000e\u0000 \u0000d\u0000e\u0000s\u0000c\u0000r\u0000i\u0000p\u0000t\u0000i\u0000o\u0000n)","source": "Figure obj 57"}],"forms": [{"index": 1,"fieldName": "list item","fieldNameRaw": "(list item)","fieldType": "Ch","tooltip": "list item","tooltipRaw": "(list item)","source": "Obj 10"},{"index": 2,"fieldName": "company_name","fieldNameRaw": "(company_name)","fieldType": "Tx","tooltip": "company_name","tooltipRaw": "(company_name)","source": "Obj 13"},{"index": 3,"fieldName": "is_client","fieldNameRaw": "(is_client)","fieldType": "Btn","tooltip": "is_client","tooltipRaw": "(is_client)","source": "Obj 15"}],"standards": [{"standard": "PDF/UA","part": "1","conformance": null,"source": "XMP"},{"standard": "PDF/A","part": "3","conformance": "A","source": "XMP"}]
}

返回的Report对象提供了对验证结果的结构化访问，使得集成到现有工作流程中变得容易。