(Unicode C++) PDF Signature Appearance Width and Height

See more PDF Signatures Examples

This example explains how the width and height of the signature appearance rectangle box is determined.

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

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#include <CkPdfW.h>
#include <CkJsonObjectW.h>
#include <CkCertW.h>

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

    CkPdfW pdf;

    // Load a PDF to be signed.
    // The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
    bool success = pdf.LoadFile(L"qa_data/pdf/hello.pdf");
    if (success == false) {
        wprintf(L"%s\n",pdf.lastErrorText());
        return;
    }

    // Options for signing are specified in JSON.
    CkJsonObjectW json;

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

    // Put the signature on page 1, top left
    json.UpdateInt(L"page",1);
    json.UpdateString(L"appearance.y",L"top");
    json.UpdateString(L"appearance.x",L"left");

    // Add some text.
    json.UpdateString(L"appearance.text[0]",L"Digitally signed by: cert_cn");
    json.UpdateString(L"appearance.text[1]",L"current_dt");

    // Add a built-in SVG graphic to the right.
    json.UpdateString(L"appearance.image",L"blue-check-mark");
    json.UpdateString(L"appearance.imagePlacement",L"right");
    json.UpdateString(L"appearance.imageOpacity",L"100");

    // There are 4 ways the width and height of the signature rectangle can be specified.
    // 1) The width and height (in points) are both explicitly specified.
    //    User space coordinates use "points" where 72 points equals 1 inch.
    //    For example (3 inches wide and 1 inch high)
    //    The fontScale is automatically chose to fit.  In addition, if a graphic (JPG or built-in SVG) is included,
    //    it is automatically scaled such that the text + graphic fit together in the specified rectangle.
    //    Note: When both height and width are explicitly specified, the resultant signature appearance rectangle
    //    will match one of the dimensions, but the other dimension will be equal or smaller.  This is because the text
    //    must be proportionally scaled.
    json.UpdateInt(L"appearance.width",72 * 3);
    json.UpdateInt(L"appearance.height",72);

    // The signature would have this appearance. In this case, the height is actually less than 1 inch because
    // if Chilkat chose a fontScale to fill the height, the resulting text's width would be too long for the desired width. 
    

    // 2) The width is explicitly specified, but we use the keyword "auto" for height.
    //    In this case, the fontScale is chosen to achieve the desired width,
    //    and the height will be whatever the result of the chosen font scale.
    //    In this example, the width is 4 inches, and the height is "auto".
    json.UpdateInt(L"appearance.width",72 * 4);
    json.UpdateString(L"appearance.height",L"auto");

    // The signature would have this appearance: 
    

    // 3) The height is explicitly specified, but we use the keyword "auto" for width.
    //    In this case, the fontScale is chosen to achieve the desired height,
    //    and the width will be whatever the result of the chosen font scale.
    //    In this example, the height is 1 inch (72 points) and the width is "auto".
    json.UpdateString(L"appearance.width",L"auto");
    json.UpdateInt(L"appearance.height",72);

    // The signature would have this appearance.
    

    // 4) Finally, we don't need to specify width/height at all.  Instead, we can choose a fontScale
    //    and the dimensions of the PDF signature appearance's rectangle will be the result of using the
    //    specified fontScale.

    CkJsonObjectW *jAppearance = json.ObjectOf(L"appearance");
    jAppearance->Delete(L"width");
    jAppearance->Delete(L"height");
    delete jAppearance;
    json.UpdateString(L"appearance.fontScale",L"10.0");

    // With fontScale = "10.0"
    

    // Load the signing certificate. (Use your own certificate.)
    CkCertW cert;
    success = cert.LoadPfxFile(L"qa_data/pfx/myPdfSigningCert.pfx",L"pfx_password");
    if (success == false) {
        wprintf(L"%s\n",cert.lastErrorText());
        return;
    }

    // Tell the pdf object to use the certificate for signing.
    success = pdf.SetSigningCert(cert);
    if (success == false) {
        wprintf(L"%s\n",pdf.lastErrorText());
        return;
    }

    success = pdf.SignPdf(json,L"qa_output/hello_signed.pdf");
    if (success == false) {
        wprintf(L"%s\n",pdf.lastErrorText());
        return;
    }

    wprintf(L"The PDF has been successfully cryptographically signed.\n");
    }