Generate 88keys sheet paper

88keys.js

const fs = require("fs");
const { PDFDocument, rgb } = require("pdf-lib");

const KEY_COLORS = "WBWBWWBWBWBW";

const KEYS = 88;
const MEASURES = 2 * 4;
const DIVISION = 3;
const SUBDIVISION = 3;

main().catch((e) => console.error(e));

async function main() {
  // Create a new PDFDocument
  const pdfDoc = await PDFDocument.create();

  // Add a blank page to the document
  const page = pdfDoc.addPage();

  // Get the width and height of the page
  const size = page.getSize();

  const hMargin = size.width * 0.05;
  const width = size.width - 2 * hMargin;

  const vMargin = size.height * 0.05;
  const height = size.height - 2 * vMargin;

  const col = width / KEYS;

  // black KEY_COLORS shades
  for (let i = 0; i < KEYS; i++) {
    const offset = hMargin + i * col;
    const pos = (i - 3 + 12) % 12;
    const isBlack = KEY_COLORS[pos] === "B";
    if (isBlack) {
      page.drawRectangle({
        x: offset + col * 0.2,
        y: vMargin,
        width: col * 0.6,
        height: height,
        color: rgb(0, 0, 0),
        borderColor: rgb(0, 0, 0),
        opacity: 0.05,
        borderOpacity: 0,
      });
    }
  }

  // vertical lines
  for (let i = 0; i <= KEYS; i++) {
    const offset = hMargin + i * col;
    const pos = (i - 3 + 12) % 12;
    const isC = pos === 0;
    const isBlack = KEY_COLORS[pos] === "B";
    const prevIsBlack = KEY_COLORS[(pos + 11) % 12] === "B";
    const isMiddleC = i === 39;
    const x = isBlack
      ? offset + col * 0.1
      : prevIsBlack
      ? offset - col * 0.1
      : offset;
    page.drawLine({
      start: { x, y: vMargin },
      end: { x, y: vMargin + height },
      thickness: isMiddleC ? 0.8 : isC ? 0.4 : 0.25,
      color: rgb(0, 0, 0),
      opacity: isC ? 0.8 : 0.5,
    });
  }

  // horizontal lines
  const horizontalLines = MEASURES * DIVISION * SUBDIVISION;
  const time = height / horizontalLines;

  for (let i = 0; i <= horizontalLines; i++) {
    const offset = vMargin + i * time;
    const isMeasure = i % (DIVISION * SUBDIVISION) === 0;
    const isDivision = !isMeasure && i % SUBDIVISION === 0;
    page.drawLine({
      start: { x: hMargin, y: offset },
      end: { x: hMargin + width, y: offset },
      thickness: isMeasure ? 0.4 : 0.25,
      color: rgb(0, 0, 0),
      opacity: isMeasure ? 0.5 : isDivision ? 0.3 : 0.1,
    });
  }

  // Serialize the PDFDocument to bytes (a Uint8Array)
  const pdfBytes = await pdfDoc.save();
  fs.writeFileSync("88keys.pdf", pdfBytes, "binary");
}