js-certificate-maker/src/pdfGenerator.js

A package to generate PDF certificates with custom names and styling

import { PDFDocument, rgb } from "pdf-lib";
import fontkit from "@pdf-lib/fontkit";
import fs from "fs";
import crypto from "crypto";
import path from "path";

const capitalize = (str, lower = false) =>
    (lower ? str.toLowerCase() : str).replace(/(?:^|\s|["'([{])+\S/g, (match) =>
        match.toUpperCase()
    );

const generatePDF = async (
    fontUrl,
    pdfTemplateUrl,
    name,
    outputDir = "output",
    fontColor = rgb(0, 0, 0), // Default black color
    xm = 0, // Default x-offset
    ym = 0 // Default y-offset
) => {
    let nameLength = name.length;
    if (nameLength > 30)
        throw new Error("Name too long. Retry with a shorter name");

    const fontBytes = fs.readFileSync(fontUrl);
    const fontSize = nameLength > 20 ? 48 : 60;
    const existingPdfBytes = fs.readFileSync(pdfTemplateUrl);
    const pdfDoc = await PDFDocument.load(new Uint8Array(existingPdfBytes));
    pdfDoc.registerFontkit(fontkit);
    const pages = pdfDoc.getPages();
    const firstPage = pages[0];
    const customFont = await pdfDoc.embedFont(
        fontBytes.buffer
    );

    const pageSize = firstPage.getSize();
    const textWidth = customFont.widthOfTextAtSize(name, fontSize);
    const textHeight = customFont.heightAtSize(fontSize);
    const pageWidth = pageSize.width;
    const pageHeight = pageSize.height;

    firstPage.drawText(name, {
        x: pageWidth / 2 - textWidth / 2 + xm,
        y: pageHeight / 2 - textHeight / 2 + ym,
        size: fontSize,
        font: customFont,
        color: fontColor,
    });

    const pdfBytes = await pdfDoc.save();
    const randomString = crypto.randomBytes(3).toString('hex');
    const fileName = `${name}-Certificate-${randomString}.pdf`;
    const outputPath = path.join(outputDir, fileName);
    fs.writeFileSync(outputPath, pdfBytes);
};

export const generateCertificates = async (
    fontUrl,
    pdfTemplateUrl,
    names,
    outputDir,
    fontColor,
    xm, 
    ym 
) => {
    console.time("Certificates");
    const capitalizedNames = names
        .map((name) => capitalize(name.trim()))
        .filter(Boolean);
    if (capitalizedNames.length === 0) {
        throw new Error("Enter at least one name correctly");
    }
    for (const name of capitalizedNames) {
        await generatePDF(
            fontUrl,
            pdfTemplateUrl,
            name,
            outputDir,
            fontColor,
            xm,
            ym
        );
    }
    console.timeEnd("Certificates");
};