Go

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. Go

    success := false

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

    pdf := chilkat.NewPdf()

    // 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 {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        return
    }

    // Options for signing are specified in JSON.
    json := chilkat.NewJsonObject()

    // 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.

    jAppearance := chilkat.NewJsonObject()
    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.)
    cert := chilkat.NewCert()
    success = cert.LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","pfx_password")
    if success == false {
        fmt.Println(cert.LastErrorText())
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jAppearance.DisposeJsonObject()
        cert.DisposeCert()
        return
    }

    // Tell the pdf object to use the certificate for signing.
    success = pdf.SetSigningCert(cert)
    if success == false {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jAppearance.DisposeJsonObject()
        cert.DisposeCert()
        return
    }

    success = pdf.SignPdf(json,"qa_output/hello_signed.pdf")
    if success == false {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jAppearance.DisposeJsonObject()
        cert.DisposeCert()
        return
    }

    fmt.Println("The PDF has been successfully cryptographically signed.")

    pdf.DisposePdf()
    json.DisposeJsonObject()
    jAppearance.DisposeJsonObject()
    cert.DisposeCert()