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. C++

#include <CkPdf.h>
#include <CkJsonObject.h>
#include <CkCert.h>

void ChilkatSample(void)
    {
    bool success = false;

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

    CkPdf pdf;

    //  Load a PDF to be signed.
    //  The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
    success = pdf.LoadFile("qa_data/pdf/hello.pdf");
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

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

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

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

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

    //  Add a built-in SVG graphic to the right.
    json.UpdateString("appearance.image","blue-check-mark");
    json.UpdateString("appearance.imagePlacement","right");
    json.UpdateString("appearance.imageOpacity","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("appearance.width",72 * 3);
    json.UpdateInt("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. 
    //  (image:https://example-code.com/images/explicit_width_height.jpg/endImage)

    //  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("appearance.width",72 * 4);
    json.UpdateString("appearance.height","auto");

    //  The signature would have this appearance: 
    //  (image:https://example-code.com/images/explicit_width_auto_height.jpg/endImage)

    //  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("appearance.width","auto");
    json.UpdateInt("appearance.height",72);

    //  The signature would have this appearance.
    //  (image:https://example-code.com/images/explicit_height_auto_width.jpg/endImage)

    //  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.

    CkJsonObject jAppearance;
    json.ObjectOf2("appearance",jAppearance);

    jAppearance.Delete("width");
    jAppearance.Delete("height");
    json.UpdateString("appearance.fontScale","10.0");

    //  With fontScale = "10.0"
    //  (image:https://example-code.com/images/font_scale_10.jpg/endImage)

    //  Load the signing certificate. (Use your own certificate.)
    CkCert cert;
    success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","pfx_password");
    if (success == false) {
        std::cout << cert.lastErrorText() << "\r\n";
        return;
    }

    //  Tell the pdf object to use the certificate for signing.
    success = pdf.SetSigningCert(cert);
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    success = pdf.SignPdf(json,"qa_output/hello_signed.pdf");
    if (success == false) {
        std::cout << pdf.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "The PDF has been successfully cryptographically signed." << "\r\n";
    }