(Perl) 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.

Chilkat Perl Downloads Perl Module for Windows, MacOS, Linux, Alpine Linux, Solaris

use chilkat();

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

$pdf = chilkat::CkPdf->new();

# 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 == 0) {
    print $pdf->lastErrorText() . "\r\n";
    exit;
}

# Options for signing are specified in JSON.
$json = chilkat::CkJsonObject->new();

# 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. 


# 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: 


# 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.


# 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 is a JsonObject
$jAppearance = $json->ObjectOf("appearance");
$jAppearance->Delete("width");
$jAppearance->Delete("height");

$json->UpdateString("appearance.fontScale","10.0");

# With fontScale = "10.0"


# Load the signing certificate. (Use your own certificate.)
$cert = chilkat::CkCert->new();
$success = $cert->LoadPfxFile("qa_data/pfx/myPdfSigningCert.pfx","pfx_password");
if ($success == 0) {
    print $cert->lastErrorText() . "\r\n";
    exit;
}

# Tell the pdf object to use the certificate for signing.
$success = $pdf->SetSigningCert($cert);
if ($success == 0) {
    print $pdf->lastErrorText() . "\r\n";
    exit;
}

$success = $pdf->SignPdf($json,"qa_output/hello_signed.pdf");
if ($success == 0) {
    print $pdf->lastErrorText() . "\r\n";
    exit;
}

print "The PDF has been successfully cryptographically signed." . "\r\n";