Grok Imagine 2.0 Ext Layers and Region Editing

task_id → segment(source_task_id) → image_id + mask_rle
        → selection_regions → region_edit → new task_id + image_id

{
  "code": 200,
  "data": {
    "id": "task_...",
    "status": "completed",
    "progress": 100,
    "cost": 0,
    "credits_cost": 0,
    "result": {
      "source_task_id": "task_...",
      "image_id": "6b78a7c3-5f9e-4a3d-a928-9e9b42113a3f",
      "image_url": "https://.../source.jpg",
      "from_cache": true,
      "cache_status": "hit",
      "objects": [{
        "index": 0,
        "name": "red sports car",
        "box_xyxy": [38.1, 689.8, 945.8, 1065.4],
        "score": 0.9765625,
        "mask_size": [1792, 1008],
        "mask_url": "",
        "mask_rle": { "size": [1792, 1008], "counts": "..." }
      }]
    }
  }
}

export interface CocoRLE {
  size: [height: number, width: number];
  counts: string;
}

export interface BinaryMask {
  width: number;
  height: number;
  data: Uint8Array; // data[y * width + x]
}

function decodeCompressedCounts(counts: string): number[] {
  const runs: number[] = [];
  let cursor = 0;
  while (cursor < counts.length) {
    let value = 0;
    let shift = 0;
    let more = true;
    while (more) {
      if (cursor >= counts.length) throw new Error("Truncated COCO RLE counts");
      const current = counts.charCodeAt(cursor++) - 48;
      value |= (current & 0x1f) << shift;
      more = (current & 0x20) !== 0;
      shift += 5;
      if (!more && (current & 0x10) !== 0) value |= -1 << shift;
    }
    if (runs.length > 2) value += runs[runs.length - 2] ?? 0;
    if (value < 0) throw new Error(\`Invalid COCO RLE run: \${value}\`);
    runs.push(value);
  }
  return runs;
}

export function decodeCocoRLE(rle: CocoRLE): BinaryMask {
  const [height, width] = rle.size;
  if (!Number.isInteger(height) || !Number.isInteger(width) || height <= 0 || width <= 0) {
    throw new Error(\`Invalid mask size: \${JSON.stringify(rle.size)}\`);
  }
  const pixelCount = width * height;
  if (!Number.isSafeInteger(pixelCount) || pixelCount > 32_000_000) {
    throw new Error(\`Mask exceeds the frontend safety limit: \${pixelCount}\`);
  }
  if (!rle.counts) throw new Error("Missing COCO RLE counts");

  const data = new Uint8Array(pixelCount);
  const runs = decodeCompressedCounts(rle.counts);
  let position = 0;
  let foreground = false;
  for (const run of runs) {
    if (position + run > data.length) throw new Error("COCO RLE exceeds mask_size");
    if (foreground) {
      for (let offset = 0; offset < run; offset++) {
        const index = position + offset;
        const y = index % height;
        const x = (index - y) / height;
        data[y * width + x] = 1;
      }
    }
    position += run;
    foreground = !foreground;
  }
  if (position !== data.length) throw new Error("COCO RLE does not cover the mask");
  return { width, height, data };
}

interface SelectionBoundary { points: number[] }
interface SelectionRegion { outer: SelectionBoundary; holes?: SelectionBoundary[] }

{
  "code": 200,
  "data": {
    "id": "task_...",
    "status": "completed",
    "progress": 100,
    "cost": 0.016,
    "credits_cost": 0.16,
    "result": {
      "images": [{
        "url": ["https://.../result.jpg"],
        "image_ids": ["<NEW_IMAGE_ID>"],
        "items": [{
          "url": "https://.../result.jpg",
          "image_id": "<NEW_IMAGE_ID>",
          "source_image_id": "<SOURCE_IMAGE_ID>",
          "role": "region_edit"
        }],
        "expires_at": 1787040000
      }]
    }
  }
}