Mozilla arch JS code

arch.js

function curveInArchCoords(col, rows, cols) {
  const mathX = col / cols * 2 * Math.PI;
  const mathY = Math.cos(mathX);
  const archY = (1 + mathY) / 2 * rows;
  return archY;
}

function setFrame(frame, rows, cols, colOffset) {
  for (const i of frame) {
    frame[i] = 0;
  }
  
  for (let col = 0; col < cols; col++) {
    const row = Math.floor(curveInArchCoords(col + colOffset, rows, cols));

    const offset = (row * cols + col) * 3;

    const red = col / cols * 255;
    const green = 0;
    const blue = row / rows * 255;

    frame[offset] = red;
    frame[offset + 1] = green;
    frame[offset + 2] = blue;
  }
}


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);
    setFrame(frame, rows, cols, second * 4);
  }
}

export default function () {
  return { transform };
}