bubblechambersimart/src/render/pdf.js

/* ============================================================
   pdf.js — single-page vector PDF writer for the print shop.
   Native PDF drawing ops (no embedded raster). Uses:
     • DeviceCMYK colour with a controllable rich black, so a
       print shop gets proper separations rather than RGB;
     • ExtGState soft-mask alpha (/ca,/CA) for true opacity on
       strokes and fills;
     • a base-14 Helvetica archival header (no font embedding).
   Geometry comes from the same scene model as every renderer.
   ============================================================ */
import { makeRng } from '../rng.js';
import { sampleBubbles, trackInkWeight } from '../scene/bubbles.js';

const MARGIN = 0.02;

export function buildPDF(scene, params, pageSize = 1728) {
  const scale = (pageSize / 2) * (1 - MARGIN);
  const cx = pageSize / 2, cy = pageSize / 2;
  const tx = (x) => (cx + x * scale);
  const ty = (y) => (cy - y * scale);            // PDF y-up
  const u = pageSize / 1000;
  const inv = params.invert;

  // CMYK colours: warm cream paper, warm rich black ink (or swapped)
  const paperCMYK = inv ? '0.04 0.06 0.16 0.00' : '0.30 0.30 0.32 1.00';
  const inkCMYK = inv ? '0.30 0.30 0.32 0.98' : '0.03 0.05 0.14 0.00';

  // ExtGState alpha registry
  const gsSet = new Map();
  const gs = (alpha) => {
    const k = Math.max(0, Math.min(100, Math.round(alpha * 100)));
    if (!gsSet.has(k)) gsSet.set(k, `GS${k}`);
    return `/GS${k} gs\n`;
  };

  let c = '';
  c += `${paperCMYK} k\n0 0 ${pageSize} ${pageSize} re f\n`;

  // chamber boundary
  if (params.showBoundary) {
    c += `q\n${gs(0.4)}${inkCMYK} K\n${(2 * u).toFixed(2)} w\n`;
    const bcx = cx, bcy = cy - pageSize * 0.35, br = pageSize * 0.45;
    const a1 = Math.PI * 0.15, a2 = Math.PI - Math.PI * 0.15, steps = 90;
    for (let i = 0; i <= steps; i++) {
      const a = Math.PI + a1 + (a2 - a1) * (i / steps);
      const px = bcx + Math.cos(a) * br, py = bcy - Math.sin(a) * br;
      c += `${px.toFixed(1)} ${py.toFixed(1)} ${i === 0 ? 'm' : 'l'}\n`;
    }
    c += `S\nQ\n`;
  }

  // instrument geometry
  if (scene.instrument) {
    c += `q\n${inkCMYK} K\n1 J\n`;
    for (const l of scene.instrument.lines)
      c += `${gs(l.opacity)}${(l.width * u).toFixed(2)} w\n${tx(l.x1).toFixed(1)} ${ty(l.y1).toFixed(1)} m ${tx(l.x2).toFixed(1)} ${ty(l.y2).toFixed(1)} l S\n`;
    for (const a of scene.instrument.arcs) {
      c += `${gs(a.opacity)}${(a.width * u).toFixed(2)} w\n${tx(a.pts[0].x).toFixed(1)} ${ty(a.pts[0].y).toFixed(1)} m\n`;
      for (let i = 1; i < a.pts.length; i++) c += `${tx(a.pts[i].x).toFixed(1)} ${ty(a.pts[i].y).toFixed(1)} l\n`;
      c += `S\n`;
    }
    c += `Q\n`;
  }

  // continuity under-strokes (bucketed by alpha)
  c += `q\n${inkCMYK} K\n1 J\n1 j\n`;
  for (const t of scene.tracks) {
    if (t.pts.length < 2) continue;
    const iw = trackInkWeight(t);
    const lw = Math.min(2.6, 0.25 + Math.sqrt(iw) * 0.12) * u * params.size * t.weight;
    if (lw < 0.2 * u) continue;
    c += `${gs(0.14 * t.weight)}${lw.toFixed(2)} w\n`;
    c += `${tx(t.pts[0].x).toFixed(2)} ${ty(t.pts[0].y).toFixed(2)} m\n`;
    for (let i = 1; i < t.pts.length; i++) c += `${tx(t.pts[i].x).toFixed(2)} ${ty(t.pts[i].y).toFixed(2)} l\n`;
    c += `S\n`;
  }
  c += `Q\n`;

  // shock
  if (scene.shock) {
    const sh = scene.shock;
    const px = tx(sh.x), py = ty(sh.y);
    c += `q\n${inkCMYK} K\n1 J\n`;
    for (const st of sh.striations) {
      const ix = px + Math.cos(st.a) * st.inner * scale, iy = py - Math.sin(st.a) * st.inner * scale;
      const ox = px + Math.cos(st.a) * st.outer * scale, oy = py - Math.sin(st.a) * st.outer * scale;
      c += `${gs(st.opacity)}${(st.width * u).toFixed(2)} w\n${ix.toFixed(1)} ${iy.toFixed(1)} m ${ox.toFixed(1)} ${oy.toFixed(1)} l S\n`;
    }
    for (const k of sh.core) {
      c += `${gs(k.opacity)}${(k.width * u).toFixed(2)} w\n${tx(k.x1).toFixed(1)} ${ty(k.y1).toFixed(1)} m ${tx(k.x2).toFixed(1)} ${ty(k.y2).toFixed(1)} l S\n`;
    }
    for (const ring of sh.rings) c += `${gs(ring.opacity)}${(ring.width * u).toFixed(2)} w\n` + strokeCircle(px, py, ring.rr * scale);
    c += `Q\n`;
  }

  // bubbles (bucketed by alpha)
  const buckets = new Map();
  const bRng = makeRng(params.seed, 'bubbles');
  for (const t of scene.tracks) {
    const key = Math.round(Math.min(1, 0.45 + t.weight * 0.5) * 20) / 20;
    if (!buckets.has(key)) buckets.set(key, []);
    buckets.get(key).push(...sampleBubbles(t, params, bRng));
  }
  c += `q\n${inkCMYK} k\n`;
  for (const [alpha, bubs] of buckets) {
    c += gs(alpha);
    for (const b of bubs) c += circlePath(tx(b.x), ty(b.y), Math.max(b.r * scale, 0.5)) + 'f\n';
  }
  c += `Q\n`;

  // plate damage
  const A = scene.artifacts;
  if (A) {
    c += `q\n${inkCMYK} K\n1 J\n`;
    for (const sc of A.scratches) c += `${gs(sc.opacity)}${(sc.width * u).toFixed(2)} w\n${tx(sc.x1).toFixed(1)} ${ty(sc.y1).toFixed(1)} m ${tx(sc.x2).toFixed(1)} ${ty(sc.y2).toFixed(1)} l S\n`;
    for (const hair of A.hairs) {
      c += `${gs(hair.opacity)}${(hair.width * u).toFixed(2)} w\n${tx(hair.pts[0].x).toFixed(1)} ${ty(hair.pts[0].y).toFixed(1)} m\n`;
      for (let i = 1; i < hair.pts.length; i++) c += `${tx(hair.pts[i].x).toFixed(1)} ${ty(hair.pts[i].y).toFixed(1)} l\n`;
      c += `S\n`;
    }
    for (const ring of A.rings) c += `${gs(ring.opacity)}${(ring.width * u).toFixed(2)} w\n` + strokeCircle(tx(ring.x), ty(ring.y), ring.r * scale);
    c += `Q\nq\n${inkCMYK} k\n`;
    for (const sp of A.specks) c += gs(sp.opacity) + circlePath(tx(sp.x), ty(sp.y), Math.max(sp.r * scale, 0.5)) + 'f\n';
    c += `Q\n`;
  }

  // fiducials
  if (params.showFiducials) {
    c += `q\n${gs(0.55)}${inkCMYK} K\n${(1.2 * u).toFixed(2)} w\n`;
    const fids = [[-0.85, -0.85], [0.85, -0.85], [-0.85, 0.85], [0.85, 0.85], [0, -0.85], [-0.85, 0], [0.85, 0]];
    const s = 8 * u;
    for (const [fx, fy] of fids) {
      const px = tx(fx), py = ty(fy);
      c += `${px - s} ${py} m ${px + s} ${py} l S\n${px} ${py - s} m ${px} ${py + s} l S\n`;
    }
    c += `Q\n`;
  }

  // archival header (Helvetica)
  if (params.showHeader) {
    const pad = 26 * u;
    c += `q\n${gs(0.6)}${inkCMYK} k\nBT\n/F0 ${(11 * u).toFixed(1)} Tf\n1 0 0 1 ${pad.toFixed(1)} ${(pageSize - pad - 11 * u).toFixed(1)} Tm (${pdfStr(scene.lab.toUpperCase())}) Tj\nET\n`;
    c += `BT\n/F0 ${(9 * u).toFixed(1)} Tf\n1 0 0 1 ${pad.toFixed(1)} ${(pageSize - pad - 27 * u).toFixed(1)} Tm (SEED ${pdfStr(params.seed)}) Tj\nET\n`;
    const fs = 10 * u;
    const rt = (txt, yoff) => {
      const wEst = txt.length * fs * 0.5;
      c += `BT\n/F0 ${fs.toFixed(1)} Tf\n1 0 0 1 ${(pageSize - pad - wEst).toFixed(1)} ${yoff.toFixed(1)} Tm (${pdfStr(txt)}) Tj\nET\n`;
    };
    rt(`PLATE ${scene.plate}`, pad + 13 * u);
    rt(`EXPOSED ${scene.exposure}`, pad);
    c += `Q\n`;
  }

  // ExtGState dict
  let extg = '';
  for (const [k, name] of gsSet) extg += `/${name} << /ca ${(k / 100).toFixed(2)} /CA ${(k / 100).toFixed(2)} >> `;

  return assemblePDF(c, pageSize, extg);
}

function circlePath(px, py, r) {
  const k = 0.5522847498 * r;
  return `${(px - r).toFixed(2)} ${py.toFixed(2)} m\n` +
    `${(px - r).toFixed(2)} ${(py + k).toFixed(2)} ${(px - k).toFixed(2)} ${(py + r).toFixed(2)} ${px.toFixed(2)} ${(py + r).toFixed(2)} c\n` +
    `${(px + k).toFixed(2)} ${(py + r).toFixed(2)} ${(px + r).toFixed(2)} ${(py + k).toFixed(2)} ${(px + r).toFixed(2)} ${py.toFixed(2)} c\n` +
    `${(px + r).toFixed(2)} ${(py - k).toFixed(2)} ${(px + k).toFixed(2)} ${(py - r).toFixed(2)} ${px.toFixed(2)} ${(py - r).toFixed(2)} c\n` +
    `${(px - k).toFixed(2)} ${(py - r).toFixed(2)} ${(px - r).toFixed(2)} ${(py - k).toFixed(2)} ${(px - r).toFixed(2)} ${py.toFixed(2)} c\n`;
}

function strokeCircle(px, py, r) {
  const k = 0.5522847498 * r;
  return `${(px - r).toFixed(2)} ${py.toFixed(2)} m ` +
    `${(px - r).toFixed(2)} ${(py + k).toFixed(2)} ${(px - k).toFixed(2)} ${(py + r).toFixed(2)} ${px.toFixed(2)} ${(py + r).toFixed(2)} c ` +
    `${(px + k).toFixed(2)} ${(py + r).toFixed(2)} ${(px + r).toFixed(2)} ${(py + k).toFixed(2)} ${(px + r).toFixed(2)} ${py.toFixed(2)} c ` +
    `${(px + r).toFixed(2)} ${(py - k).toFixed(2)} ${(px + k).toFixed(2)} ${(py - r).toFixed(2)} ${px.toFixed(2)} ${(py - r).toFixed(2)} c ` +
    `${(px - k).toFixed(2)} ${(py - r).toFixed(2)} ${(px - r).toFixed(2)} ${(py - k).toFixed(2)} ${(px - r).toFixed(2)} ${py.toFixed(2)} c S\n`;
}

function pdfStr(s) { return String(s).replace(/([()\\])/g, '\\$1'); }

function assemblePDF(content, pageSize, extg) {
  const enc = new TextEncoder();
  const contentBytes = enc.encode(content);
  let body = `%PDF-1.4\n%\xC3\xA0\xC3\xA1\xC3\xA2\xC3\xA3\n`;
  const offsets = [];
  const addObj = (s) => { offsets.push(body.length); body += s; };
  const resources = `<< /ExtGState << ${extg} >> /Font << /F0 << /Type /Font /Subtype /Type1 /BaseFont /Helvetica >> >> >>`;
  addObj(`1 0 obj\n<< /Type /Catalog /Pages 2 0 R >>\nendobj\n`);
  addObj(`2 0 obj\n<< /Type /Pages /Kids [3 0 R] /Count 1 >>\nendobj\n`);
  addObj(`3 0 obj\n<< /Type /Page /Parent 2 0 R /MediaBox [0 0 ${pageSize} ${pageSize}] /Contents 4 0 R /Resources ${resources} >>\nendobj\n`);
  addObj(`4 0 obj\n<< /Length ${contentBytes.length} >>\nstream\n${content}\nendstream\nendobj\n`);
  const xref = body.length;
  body += `xref\n0 5\n0000000000 65535 f \n`;
  for (const o of offsets) body += String(o).padStart(10, '0') + ' 00000 n \n';
  body += `trailer\n<< /Size 5 /Root 1 0 R >>\nstartxref\n${xref}\n%%EOF\n`;
  return new Uint8Array(enc.encode(body));
}