Rust Requires Chilkat v11.0.0+

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. Rust

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

let pdf = chilkat::Pdf::new();

// Load a PDF to be signed.
// The "hello.pdf" is available at https://chilkatsoft.com/hello.pdf
if pdf.load_file("qa_data/pdf/hello.pdf").is_err() {
    println!("{}", pdf.last_error_text());
    return;
}

// Options for signing are specified in JSON.
let json = chilkat::JsonObject::new();

// In most cases, the signingCertificateV2 and signingTime attributes are required.
let _ = json.update_int("signingCertificateV2", 1);
let _ = json.update_int("signingTime", 1);

// Put the signature on page 1, top left
let _ = json.update_int("page", 1);
let _ = json.update_string("appearance.y", "top");
let _ = json.update_string("appearance.x", "left");

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

// Add a built-in SVG graphic to the right.
let _ = json.update_string("appearance.image", "blue-check-mark");
let _ = json.update_string("appearance.imagePlacement", "right");
let _ = json.update_string("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.
let _ = json.update_int("appearance.width", 72 * 3);
let _ = json.update_int("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".
let _ = json.update_int("appearance.width", 72 * 4);
let _ = json.update_string("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".
let _ = json.update_string("appearance.width", "auto");
let _ = json.update_int("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.

let j_appearance = chilkat::JsonObject::new();
let _ = json.object_of2("appearance", &j_appearance);

let _ = j_appearance.delete("width");
let _ = j_appearance.delete("height");
let _ = json.update_string("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.)
let cert = chilkat::Cert::new();
if cert.load_pfx_file("qa_data/pfx/myPdfSigningCert.pfx", "pfx_password").is_err() {
    println!("{}", cert.last_error_text());
    return;
}

// Tell the pdf object to use the certificate for signing.
if pdf.set_signing_cert(&cert).is_err() {
    println!("{}", pdf.last_error_text());
    return;
}

if pdf.sign_pdf(&json, "qa_output/hello_signed.pdf").is_err() {
    println!("{}", pdf.last_error_text());
    return;
}

println!("The PDF has been successfully cryptographically signed.");