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

void ChilkatSample(void)
    {
    HCkPdf pdf;
    BOOL success;
    HCkJsonObject json;
    HCkJsonObject jAppearance;
    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");

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

    // Add a built-in SVG graphic to the right.
    CkJsonObject_UpdateString(json,"appearance.image","blue-check-mark");
    CkJsonObject_UpdateString(json,"appearance.imagePlacement","right");
    CkJsonObject_UpdateString(json,"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.
    CkJsonObject_UpdateInt(json,"appearance.width",72 * 3);
    CkJsonObject_UpdateInt(json,"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".
    CkJsonObject_UpdateInt(json,"appearance.width",72 * 4);
    CkJsonObject_UpdateString(json,"appearance.height","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".
    CkJsonObject_UpdateString(json,"appearance.width","auto");
    CkJsonObject_UpdateInt(json,"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.

    jAppearance = CkJsonObject_ObjectOf(json,"appearance");
    CkJsonObject_Delete(jAppearance,"width");
    CkJsonObject_Delete(jAppearance,"height");
    CkJsonObject_Dispose(jAppearance);
    CkJsonObject_UpdateString(json,"appearance.fontScale","10.0");

    // With fontScale = "10.0"
    

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

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


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

    }