arch.js

// Example of the JavaScript module for the Arc project.

let bytes;
let slicePtr = 0;

function yellow(line, i) {
  line[i + 1] = line[i] = 255;
  line[i + 2] = 0;
}

function blue(line, i) {
  line[i + 1] = line[i] = 0;
  line[i + 2] = 255;
}

function setFrameByBytes(frame, rows, cols, bytes) {
  let bytePtr = 0;
  let bitPtr = 0;
  for (let i = 0; i < rows; i++) {
    const lineSize = cols * 3;
    const line = frame.subarray(lineSize * i, lineSize * (i + 1));

    for (let j = 0; j < cols; j++) {
      if (bytes[bytePtr]) {
        yellow(line, j * 3);
      } else {
        blue(line, j * 3);
      }
    }
    bytePtr++;
  }
}

export function transform(buffer, rows, cols, frameCount, fps, isFirst) {
  const frameSize = 3 * rows * cols;
  for (let i = 0; i < frameCount; i++) {
    const second = i / fps;
    const frame = new Uint8Array(buffer, frameSize * i, frameSize);
    setFrameByBytes(
      frame,
      rows,
      cols,
      bytes.subarray(slicePtr, slicePtr + rows)
    );
    slicePtr++;
  }
}

function toBits(acc, curr) {
  for (let i = 7; i >= 0; i--) {
    acc.push(curr << i & 1);
  }

  return acc;
}


export default function() {
  return fetch('https://2018.jsconf.eu/')
    .then(res => res.arrayBuffer())
    .then(res => {
      bytes = Uint8Array.from(new Uint8Array(res).reduce(toBits, []))

      return Promise.resolve({
        transform,
      });
    });
}