本次发布的新功能

  • [功能] Image digital signature support and validation (SIGNATURENET‑5528)
    引入基于隐写术的数字签名嵌入到 PNG 和 JPG 图像中。支持密码保护的签名、流/文件处理，并提供可选检测阈值的完整验证。

  • [增强] LINQ queries optimization for signature operations (SIGNATURENET‑5500)
    重构库中的 LINQ 逻辑以减少内存分配并提升执行速度。为 Search 和 Verify 方法添加基于谓词的过滤，使开发者能够在耗时处理之前预过滤签名。

修复与增强

  • [Bug Fix] Fixed GeneratePreview() type initializer exception with DOC format on Linux (SIGNATURENET‑5555)
    在 Linux 环境下为 Microsoft Word 文档生成预览时，不再抛出异常。

如何使用新功能

对图像进行签名（隐写术）

using GroupDocs.Signature;
using GroupDocs.Signature.Options;

string inputFile  = "image.png";
string outputFile = "signed_image.png";
string password   = "MySecurePassword123";

using (Signature signature = new Signature(inputFile))
{
    ImageDigitalSignOptions signOptions = new ImageDigitalSignOptions
    {
        Password = password
    };

    SignResult signResult = signature.Sign(outputFile, signOptions);

    if (signResult.Succeeded?.Count > 0)
    {
        Console.WriteLine("Image signed successfully!");
        Console.WriteLine($"Signatures added: {signResult.Succeeded.Count}");
    }
}

验证已签名的图像

using GroupDocs.Signature;
using GroupDocs.Signature.Options;

string signedFile = "signed_image.png";
string password   = "MySecurePassword123";

using (Signature signature = new Signature(signedFile))
{
    ImageDigitalVerifyOptions verifyOptions = new ImageDigitalVerifyOptions
    {
        Password = password,
        DetectionThresholdPercent = 75   // optional, 0‑100%
    };

    VerificationResult verifyResult = signature.Verify(verifyOptions);

    if (verifyResult.IsValid)
    {
        Console.WriteLine("Digital signature is valid!");
        Console.WriteLine($"Verified signatures: {verifyResult.Succeeded.Count}");
    }
    else
    {
        Console.WriteLine("Digital signature is invalid or not found.");
    }
}

使用完整数据提取的高级验证

using (Signature signature = new Signature("signed_image.png"))
{
    ImageDigitalVerifyOptions verifyOptions = new ImageDigitalVerifyOptions
    {
        Password = "MySecurePassword123",
        UseFullDataExtraction = true,          // maximum accuracy
        DetectionThresholdPercent = 85
    };

    VerificationResult verifyResult = signature.Verify(verifyOptions);

    if (verifyResult.IsValid && verifyOptions.DetectedProbability.HasValue)
    {
        Console.WriteLine($"Signature detected with {verifyOptions.DetectedProbability.Value}% probability");
    }
}

使用谓词的 LINQ 优化搜索

using GroupDocs.Signature;
using GroupDocs.Signature.Options;
using GroupDocs.Signature.Domain;

using (Signature signature = new Signature("document.pdf"))
{
    List<SearchOptions> searchOptions = new List<SearchOptions>
    {
        new TextSearchOptions()
    };

    // Filter only text signatures containing "Approved"
    SearchResult result = signature.Search(searchOptions,
        sig => sig is TextSignature txt && txt.Text.Contains("Approved"));

    foreach (BaseSignature sig in result.Signatures)
    {
        Console.WriteLine($"Found: {((TextSignature)sig).Text}");
    }
}

使用谓词的 LINQ 优化验证

using (Signature signature = new Signature("signed_document.pdf"))
{
    TextVerifyOptions verifyOptions = new TextVerifyOptions("John Smith");

    // Verify only signatures on page 1
    List<BaseSignature> result = signature.Verify(verifyOptions,
        sig => sig.PageNumber == 1);

    Console.WriteLine($"Found {result.Count} verified signatures on page 1");
}

如何获取更新

  • NuGet – 升级到最新的 GroupDocs.Signature 包： 
    dotnet add package GroupDocs.Signature --version 25.12
  • 直接下载 – 从官方发布页面获取 .NET 编译好的程序集：
    GroupDocs.Signature for .NET 25.12 DLLs

资源