Zig

PDF Signature Appearance Text Substitution Keywords

See more PDF Signatures Examples

This example demonstrates the text substitution keywords that can be used in the PDF signature's appearance text.

Note: This example requires Chilkat v9.5.0.85 or greater.

Zig

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

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

    const pdf = try chilkat.Pdf.init();
    defer pdf.deinit();

    // Load a PDF to be signed.
    pdf.loadFile("qa_data/pdf/empty.pdf") catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    // Options for signing are specified in JSON.
    const json = try chilkat.JsonObject.init();
    defer json.deinit();

    // In most cases, the signingCertificateV2 and signingTime attributes are required.
    json.updateInt("signingCertificateV2", 1) catch {};
    json.updateInt("signingTime", 1) catch {};

    // Put the signature on page 1, top left
    json.updateInt("page", 1) catch {};
    json.updateString("appearance.y", "top") catch {};
    json.updateString("appearance.x", "left") catch {};

    // Use a font scale of 7.0
    json.updateString("appearance.fontScale", "7.0") catch {};

    // The appearance of the PDF signature can contain any number of text lines.
    // Chilkat has defined a number of special keywords that can be used in any text line.
    // Each keyword is replaced with the actual value.
    // For example, "cert_cn" is replaced with the certificate subject's common name (CN).

    // Here we are creating a signature with many lines of text, to demonstrate each
    // keyword.
    json.updateString("appearance.text[0]", "Date/time in PDF format: current_dt") catch {};
    json.updateString("appearance.text[1]", "Current Local date/time: current_datetime") catch {};
    json.updateString("appearance.text[2]", "GMT Timestamp: current_timestamp_gmt") catch {};
    json.updateString("appearance.text[3]", "Local Timestamp: current_timestamp_local") catch {};
    json.updateString("appearance.text[4]", "GMT RFC822 date/time: current_rfc822_dt_gmt") catch {};
    json.updateString("appearance.text[5]", "Local RFC822 date/time: current_rfc822_dt_local") catch {};
    json.updateString("appearance.text[6]", "Cert DN (Distinguished Name): cert_dn") catch {};
    json.updateString("appearance.text[7]", "Cert Common Name: cert_cn") catch {};
    json.updateString("appearance.text[8]", "Cert Organizational ID (2.5.4.97): cert_org_id") catch {};
    json.updateString("appearance.text[9]", "Cert Email: cert_email") catch {};
    json.updateString("appearance.text[10]", "Cert Organization: cert_organization") catch {};
    json.updateString("appearance.text[11]", "Cert Organziational Unit: cert_ou") catch {};
    json.updateString("appearance.text[12]", "Cert State: cert_state") catch {};
    json.updateString("appearance.text[13]", "Cert Country: cert_country") catch {};
    json.updateString("appearance.text[14]", "Cert Locality: cert_locality") catch {};
    json.updateString("appearance.text[15]", "Cert Serial Number (hex): cert_serial_hex") catch {};
    json.updateString("appearance.text[16]", "Cert Serial Number (decimal): cert_serial_dec") catch {};
    json.updateString("appearance.text[17]", "Cert Thumbprint: cert_thumbprint") catch {};
    json.updateString("appearance.text[18]", "Cert Issuer Common Name: cert_issuer_cn") catch {};

    const jpg_data = try chilkat.BinData.init();
    defer jpg_data.deinit();
    jpg_data.loadFile("qa_data/jpg/seal1.jpg") catch {
        std.debug.print("Failed to load the JPG image.\n", .{});
        return;
    };

    pdf.setSignatureJpeg(jpg_data) catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    // Specify that we want to display the JPG image in the center with 33% opacity.
    json.updateString("appearance.image", "custom-jpg") catch {};
    json.updateString("appearance.imagePlacement", "center") catch {};
    json.updateString("appearance.imageOpacity", "33") catch {};

    // Load the signing certificate. (Use your own certificate.)
    const cert = try chilkat.Cert.init();
    defer cert.deinit();
    cert.loadPfxFile("qa_data/pfx/myPdfSigningCert.pfx", "pfx_password") catch {
        std.debug.print("{s}\n", .{try cert.getLastErrorText(alloc)});
        return;
    };

    // Tell the pdf object to use the certificate for signing.
    pdf.setSigningCert(cert) catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    pdf.signPdf(json, "qa_output/hello_signed.pdf") catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("The PDF has been successfully cryptographically signed.\n", .{});

    // The appearance of the signature appears in Adobe Acrobat as shown here:

    // (image:https://example-code.com/images/pdf_signature_text_replacements.jpg/endImage)
}