Function findClusterSize

test/unit/visual/visualTest.js:266–359

* Find the size of a connected cluster of diff pixels using BFS

(
  pixels,
  startX, startY,
  width, height,
  radius,
  visited
)

 * Find the size of a connected cluster of diff pixels using BFS
 */
function findClusterSize(
  pixels,
  startX, startY,
  width, height,
  radius,
  visited
) {
  const queue = [{ x: startX, y: startY }];
  let size = 0;
  const clusterPixels = [];

  while (queue.length > 0) {
    const { x, y } = queue.shift();
    const pos = (y * width + x) * 4;

    // Skip if already visited
    if (visited.has(pos)) continue;

    // Skip if not a diff pixel
    if (
      pixels[pos] !== 255 ||
      pixels[pos + 1] !== 0 ||
      pixels[pos + 2] !== 0
    ) continue;

    // Mark as visited
    visited.add(pos);
    size++;
    clusterPixels.push({ x, y });

    // Add neighbors to queue
    for (let dy = -radius; dy <= radius; dy++) {
      for (let dx = -radius; dx <= radius; dx++) {
        const nx = x + dx;
        const ny = y + dy;

        // Skip if out of bounds
        if (nx < 0 || nx >= width || ny < 0 || ny >= height) continue;

        // Skip if already visited
        const npos = (ny * width + nx) * 4;
        if (!visited.has(npos)) {
          queue.push({ x: nx, y: ny });
        }
      }
    }
  }

  let isLineShift = false;
  if (clusterPixels.length > 0) {
    // Count pixels with limited neighbors (line-like characteristic)
    let linelikePixels = 0;

    for (const { x, y } of clusterPixels) {
      // Count neighbors
      let neighbors = 0;
      for (let dy = -1; dy <= 1; dy++) {
        for (let dx = -1; dx <= 1; dx++) {