@thi.ng/pixel-io-netpbm/write.js

Multi-format NetPBM reader & writer support for @thi.ng/pixel

import { GRAY16 } from "@thi.ng/pixel/format/gray16";
const __formatComments = (comments = ["generated by @thi.ng/pixel-io-netpbm"]) => comments.map((x) => `# ${x}`).join("\n");
const __luminance = (c) => ((c >>> 16 & 255) * 29 + (c >>> 8 & 255) * 150 + (c & 255) * 76) / 255;
const __initHeader = (magic, limits, size, buf, comments) => {
  const { width, height } = buf;
  let header = magic + "\n";
  const comm = __formatComments(comments);
  if (comm.length) header += comm + "\n";
  header += `${width} ${height}
`;
  if (limits > 0) header += limits + "\n";
  const dest = new Uint8Array(size + header.length);
  dest.set([...header].map((x) => x.charCodeAt(0)));
  return { dest, start: header.length, abgr: buf.format.toABGR };
};
const asPBM = (buf, comments) => {
  const { data, width, height } = buf;
  const { dest, start, abgr } = __initHeader(
    "P4",
    0,
    Math.ceil(width / 8) * height,
    buf,
    comments
  );
  const w1 = width - 1;
  for (let y = 0, i = start, j = 0; y < height; y++) {
    for (let x = 0, b = 0; x <= w1; x++, j++) {
      const xx = ~x & 7;
      if (__luminance(abgr(data[j])) < 128) {
        b |= 1 << xx;
      }
      if (xx === 0 || x === w1) {
        dest[i++] = b;
        b = 0;
      }
    }
  }
  return dest;
};
const asPGM = (buf, comments) => {
  const { data, width, height } = buf;
  const { dest, start, abgr } = __initHeader(
    "P5",
    255,
    width * height,
    buf,
    comments
  );
  for (let i = start, j = 0; j < data.length; i++, j++) {
    dest[i] = __luminance(abgr(data[j]));
  }
  return dest;
};
const asPGM16 = (buf, comments) => {
  if (buf.format !== GRAY16) buf = buf.as(GRAY16);
  const { data, width, height } = buf;
  const { dest, start } = __initHeader(
    "P5",
    65535,
    width * height * 2,
    buf,
    comments
  );
  for (let i = start, j = 0; j < data.length; i += 2, j++) {
    dest[i] = data[j] >> 8;
    dest[i + 1] = data[j] & 255;
  }
  return dest;
};
const asPPM = (buf, comments) => {
  const { data, width, height } = buf;
  const { dest, start, abgr } = __initHeader(
    "P6",
    255,
    width * 3 * height,
    buf,
    comments
  );
  for (let i = start, j = 0; j < data.length; i += 3, j++) {
    const col = abgr(data[j]);
    dest[i] = col & 255;
    dest[i + 1] = col >> 8 & 255;
    dest[i + 2] = col >> 16 & 255;
  }
  return dest;
};
export {
  asPBM,
  asPGM,
  asPGM16,
  asPPM
};