(C) PDF Signature with Background Image (Seal/Stamp/etc.)

See more PDF Signatures Examples

Demonstrates how to sign a PDF with an appearance that includes a background image, such as a seal, stamp, etc.

Note: This example requires Chilkat v9.5.0.85 or greater.

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#include <C_CkPdf.h>
#include <C_CkJsonObject.h>
#include <C_CkBinData.h>
#include <C_CkCert.h>

void ChilkatSample(void)
    {
    HCkPdf pdf;
    BOOL success;
    HCkJsonObject json;
    HCkBinData jpgData;
    HCkCert cert;

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    pdf = CkPdf_Create();

    // Load a PDF to be signed.
    // The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
    success = CkPdf_LoadFile(pdf,"qa_data/pdf/hello.pdf");
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf));
        CkPdf_Dispose(pdf);
        return;
    }

    // Options for signing are specified in JSON.
    json = CkJsonObject_Create();

    // In most cases, the signingCertificateV2 and signingTime attributes are required.
    CkJsonObject_UpdateInt(json,"signingCertificateV2",1);
    CkJsonObject_UpdateInt(json,"signingTime",1);

    // Put the signature on page 1, top left
    CkJsonObject_UpdateInt(json,"page",1);
    CkJsonObject_UpdateString(json,"appearance.y","top");
    CkJsonObject_UpdateString(json,"appearance.x","left");

    // Use a font scale of 10.0
    CkJsonObject_UpdateString(json,"appearance.fontScale","10.0");

    // In this example, the appearance of the digital signature will contain three lines:
    // 1) The signing certificate's common name
    // 2) The current date/time
    // 3) Some arbitrary text.
    // The keyword "cert_cn" is replaced with the Certificate's Subject Common Name.
    // The keyword "current_dt" is replaced with the current date/time.
    // Any number of appearance text lines can be added.
    CkJsonObject_UpdateString(json,"appearance.text[0]","Digitally signed by: cert_cn");
    CkJsonObject_UpdateString(json,"appearance.text[1]","current_dt");
    CkJsonObject_UpdateString(json,"appearance.text[2]","The crazy brown fox jumps over the lazy dog.");

    // Load a JPG image to be shown with 30% opacity in the background.
    // (the image must be in the JPG format)
    // The sample university.jpb is available at https://example-code.com/images/university.jpg

    jpgData = CkBinData_Create();
    success = CkBinData_LoadFile(jpgData,"qa_data/jpg/university.jpg");
    if (success == FALSE) {
        printf("Failed to load the JPG image.\n");
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkBinData_Dispose(jpgData);
        return;
    }

    success = CkPdf_SetSignatureJpeg(pdf,jpgData);
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf));
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkBinData_Dispose(jpgData);
        return;
    }

    // Specify that we want to display the JPG image in the center with 30% opacity.
    CkJsonObject_UpdateString(json,"appearance.image","custom-jpg");
    CkJsonObject_UpdateString(json,"appearance.imagePlacement","center");
    CkJsonObject_UpdateString(json,"appearance.imageOpacity","30");

    // Load the signing certificate. (Use your own certificate.)
    cert = CkCert_Create();
    success = CkCert_LoadPfxFile(cert,"qa_data/pfx/myPdfSigningCert.pfx","secret");
    if (success == FALSE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkBinData_Dispose(jpgData);
        CkCert_Dispose(cert);
        return;
    }

    // Tell the pdf object to use the certificate for signing.
    success = CkPdf_SetSigningCert(pdf,cert);
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf));
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkBinData_Dispose(jpgData);
        CkCert_Dispose(cert);
        return;
    }

    success = CkPdf_SignPdf(pdf,json,"qa_output/hello_signed.pdf");
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf));
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkBinData_Dispose(jpgData);
        CkCert_Dispose(cert);
        return;
    }

    printf("The PDF has been successfully cryptographically signed.\n");

    // The appearance of the signature appears in Adobe Acrobat as shown below.
    // The JPG is automatically scaled to the size of the signature based on the signature's font scale
    // and number of text lines.
    


    CkPdf_Dispose(pdf);
    CkJsonObject_Dispose(json);
    CkBinData_Dispose(jpgData);
    CkCert_Dispose(cert);

    }