Updating Image signatures with advanced options

GroupDocs.Signature provides ImageSignature class to manipulate image signatures location, and size over Update method of Signature class. This method returns UpdateResult object to analyze if signatures were successfully processed.

Please be aware that Update method modifies the same document that was passed to constructor of Signature class. The UpdateResult contains list of successfully updated signatures and ones that failed. The Image signature could be failed to update due to several reasons:

  • if signature object was initialized with constructor by incorrect signature identifier;
  • if signature object was not found;
  • there was an error occurred while updating signature in the document.

Here are the steps to update Image signature in the document with GroupDocs.Signature:

  • Create new instance of Signature class and pass source document path as a constructor parameter;
  • Instantiate ImageSearchOptions object with desired properties;
  • Call Search method to obtain list of ImageSignatures;
  • Select from list ImageSignature object(s) that should be updated;
  • Call Signature object Update method and pass one or several signatures to it.
  • Analyze UpdateResult result to check whether signatures were updated or not.

Here are the alternative steps to update Image signature in the document with GroupDocs.Signature. This approach is based on saved signatures Id after Search or Sign methods.

  • Create new instance of Signature class and pass source document path as a constructor parameter;
  • Instantiate one or several ImageSignature objects with signature Id(s) passed to constructor;
  • Call Signature class object Update method and pass one or several signatures to it;
  • Analyze UpdateResult result to check whether signatures were updated or not. 

The following table describes changeable properties for Image signatures dependent on document type.

Document Type / Signature PropertyLeftTopWidthHeightSizeIsSignature
Image(error)(error)(error)(error)(error)(error)
Spreadsheet(tick)(tick)(tick)(tick)(error)(tick)
Pdf(tick)(tick)(tick)(tick)(error)(tick)
Presentation(tick)(tick)(tick)(tick)(error)(tick)
Word Processing(tick)(tick)(tick)(tick)(error)(tick)

This example shows how to update Image signature that was found using Search method.

using (Signature signature = new Signature("sampleSigned.xlsx"))
{
    ImageSearchOptions options = new ImageSearchOptions();
    // search for image signatures in document
    List<ImageSignature> signatures = signature.Search<ImageSignature>(options);
    // adjust signature properties
    foreach (ImageSignature temp in signatures)
    {
        // apply some condition to adjust signature properties
        temp.Left = temp.Left + 10;
        temp.Top = temp.Top + 10;
        if (temp.Size > 10000)
        {
            temp.IsSignature = false;
        }
    }
    // update all found signatures
    UpdateResult updateResult = signature.Update(signatures.ConvertAll(p => (BaseSignature)p));
    if (updateResult.Succeeded.Count == signatures.Count)
    {
        Console.WriteLine("All signatures were successfully updated!");
    }
    else
    {
        Console.WriteLine($"Successfully updated signatures : {updateResult.Succeeded.Count}");
        Console.WriteLine($"Not updated signatures : {updateResult.Failed.Count}");
    }
    Console.WriteLine("List of updated signatures:");
    foreach (BaseSignature temp in updateResult.Succeeded)
    {
        Console.WriteLine($"Signature# Id:{temp.SignatureId}, Location: {temp.Left}x{temp.Top}. Size: {temp.Width}x{temp.Height}");
    }
}

Update Image signature in document by known signature Identifier

This example shows how to update Image signature in the document by known signature Id (that was obtained by Search or Sign method previously).

// initialize Signature instance
using (Signature signature = new Signature("sampleSigned.pdf"))
{
    // read from some data source signature Id value
    string[] signatureIdList = new string[]
    {
        "1dd21cf3-b904-4da9-9413-1ff1dab51974",
        "9e386726-a773-4971-b2fc-eaadfce65ffd"
    };
    // create list of Image Signature by known SignatureId
    List<BaseSignature> signatures = new List<BaseSignature>();
    signatureIdList.ToList().ForEach(p => signatures.Add(new ImageSignature(p)));
    // update all found signatures
    UpdateResult updateResult = signature.Update(signatures);
    if (updateResult.Succeeded.Count == signatures.Count)
    {
        Console.WriteLine("All signatures were successfully updated!");
    }
    else
    {
        Console.WriteLine($"Successfully updated signatures : {updateResult.Succeeded.Count}");
        Console.WriteLine($"Not updated signatures : {updateResult.Failed.Count}");
    }
    Console.WriteLine("List of updated signatures:");
    foreach (BaseSignature temp in updateResult.Succeeded)
    {
        Console.WriteLine($"Signature# Id:{temp.SignatureId}, Location: {temp.Left}x{temp.Top}. Size: {temp.Width}x{temp.Height}");
    }
}

More resources

GitHub Examples

You may easily run the code above and see the feature in action in our GitHub examples:

Free Online App 

Along with full-featured .NET library we provide simple, but powerful free Apps.
You are welcome to eSign PDF, Word, Excel, PowerPoint documents with free to use online GroupDocs Signature App.