Generate signature preview

GroupDocs.Signature provides PreviewSignatureOptions class to specify different options to manage signatures preview generation process.

Here are the steps to generate signature preview with GroupDocs.Signature:

Instantiate the required SignOptions object with the settings you want to generate the preview
Instantiate the PreviewSignatureOptions object with:
delegate for signature stream creation (see interface PageSignatureStreamFactory);
image preview format - PNG / JPG / BMP,
unique signature identifier.

Stream that were created by createSignatureStream delegate will be disposed automatically once after generation of preview image. If you need to implement custom image preview stream disposing you have to pass additional argument closeSignatureStream to clean up resources.

Call the static method generateSignaturePreview method of Signature and pass PreviewSignatureOptions to it.

CreateSignatureStream delegate implementation

GroupDocs.Signature expects createSignatureStream delegate to obtain each signature stream for image preview generation process

private static OutputStream createSignatureStream(PreviewSignatureOptions previewOptions)
    {
        try {
            Path path = Paths.get("C:\\Output\\GenerateSignaturePreviewAdvanced\\");
            if (!Files.exists(path)) {

                Files.createDirectory(path);
                System.out.println("Directory created");
            } else {

                System.out.println("Directory already exists");
            }
            File imageFilePath = new File(path+"\\signature"+previewOptions.getSignatureId()+"-"+previewOptions.getSignOptions().getSignatureType()+".jpg");
            return new FileOutputStream(imageFilePath);
        }catch (Exception e) {
            throw new RuntimeException(e.getMessage());
        }

    }

ReleaseSignatureStream delegate implementation

 private static void releaseSignatureStream(PreviewSignatureOptions previewOptions, OutputStream signatureStream)
    {
        try {
            signatureStream.close();
            String imageFilePath = new File("C:\\Output\\GenerateSignaturePreviewAdvanced\\\\signature"+previewOptions.getSignatureId()+"-"+previewOptions.getSignOptions().getSignatureType()+".jpg").getPath();
            System.out.print("Image file "+imageFilePath+" is ready for preview");
        }catch (Exception e){
            throw new RuntimeException(e.getMessage());
        }
    }

Generate signature preview

public static void GetPreview()
{
    // create options
    QrCodeSignOptions signOptions = new QrCodeSignOptions();
        {
            signOptions.setEncodeType(QrCodeTypes.QR);
                // setup Data property with Address object
            Address address = new Address();
            address.setStreet("221B Baker Street");
            address.setCity("London");
            address.setState("NW");
            address.setZIP("NW16XE");
            address.setCountry("England");
            signOptions.setData(address);
                // set right bottom corner
            signOptions.setHorizontalAlignment(HorizontalAlignment.Left);
            signOptions.setVerticalAlignment(VerticalAlignment.Center);
            signOptions.setWidth(100);
            signOptions.setHeight(100);
            signOptions.setMargin(new Padding(10));
        };

        // create signature preview options object
        PreviewSignatureOptions previewOption = new PreviewSignatureOptions(signOptions, new PageSignatureStreamFactory() {
            @Override
            public OutputStream createSignatureStream(PreviewSignatureOptions previewOptions) {
                return generateSignatureStream(previewOptions);
            }

            @Override
            public void closeSignatureStream(PreviewSignatureOptions previewOptions, OutputStream pageStream) {
                releaseSignatureStream(previewOptions, pageStream);
            }
        });
        previewOption.setSignatureId(UUID.randomUUID().toString());
        previewOption.setPreviewFormat(PreviewFormats.JPEG);

        // generate preview
        Signature.generateSignaturePreview(previewOption);
}

    private static OutputStream generateSignatureStream(PreviewSignatureOptions previewOptions)
    {
        try {
            Path path = Paths.get(Constants.OutputPath, "\\GenerateSignaturePreviewAdvanced\\");
            if (!Files.exists(path)) {

                Files.createDirectory(path);
                System.out.println("Directory created");
            } else {

                System.out.println("Directory already exists");
            }
            File imageFilePath = new File(path+"\\signature"+previewOptions.getSignatureId()+"-"+previewOptions.getSignOptions().getSignatureType()+".jpg");
            return new FileOutputStream(imageFilePath);
        }catch (Exception e) {
            throw new RuntimeException(e.getMessage());
        }
    }

    private static void releaseSignatureStream(PreviewSignatureOptions previewOptions, OutputStream signatureStream)
    {
        try {
            signatureStream.close();
            String imageFilePath = new File(Constants.OutputPath + "\\GeneratePreviewHideSignatures\\signature"+previewOptions.getSignatureId()+"-"+previewOptions.getSignOptions().getSignatureType()+".jpg").getPath();
            System.out.print("Image file "+imageFilePath+" is ready for preview");
        }catch (Exception e){
            throw new RuntimeException(e.getMessage());
        }
    }

Advanced Usage Topics

To learn more about document eSign features, please refer to the advanced usage section.

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.

Generate document pages preview Update signatures in documents