Rork Max で iMessage 拡張を作り、アプリの世界観をメッセージに持ち込む — 配布導線としての実装メモ

// imessage-memory.mjs — デコード後のビットマップがどれだけ場所を取るか
const MB = 1024 * 1024;
const BUDGET_MB = 40;                            // 拡張プロセスに置く自前の予算
 
const source = { w: 1290, h: 2796 };             // 原寸の壁紙
const cellPt = 110, scale = 3;                   // グリッド1枠 110pt を @3x で描く
const thumb = { w: cellPt * scale, h: Math.round(cellPt * scale * (source.h / source.w)) };
 
const bytes = (s) => s.w * s.h * 4;              // RGBA8
const fits = (s) => Math.floor((BUDGET_MB * MB) / bytes(s));
 
console.log(`per-image full=${(bytes(source) / MB).toFixed(2)}MB thumb=${(bytes(thumb) / MB).toFixed(2)}MB`);
console.log(`fits full=${fits(source)} thumb=${fits(thumb)}`);
for (const n of [6, 12, 24, 48]) {
  console.log(`${n} | ${((n * bytes(source)) / MB).toFixed(1)} | ${((n * bytes(thumb)) / MB).toFixed(1)}`);
}

import ImageIO
import UIKit
 
// 「読み込んでから縮める」のではなく、小さくデコードする
func downsample(_ url: URL, to pointSize: CGSize, scale: CGFloat) -> UIImage? {
    let srcOptions = [kCGImageSourceShouldCache: false] as CFDictionary
    guard let src = CGImageSourceCreateWithURL(url as CFURL, srcOptions) else { return nil }
 
    let maxPixel = max(pointSize.width, pointSize.height) * scale
    let options = [
        kCGImageSourceCreateThumbnailFromImageAlways: true,
        kCGImageSourceShouldCacheImmediately: true,
        kCGImageSourceCreateThumbnailWithTransform: true,
        kCGImageSourceThumbnailMaxPixelSize: maxPixel,
    ] as CFDictionary
 
    guard let cg = CGImageSourceCreateThumbnailAtIndex(src, 0, options) else { return nil }
    return UIImage(cgImage: cg, scale: scale, orientation: .up)
}

import Messages
 
final class MessagesViewController: MSMessagesAppViewController {
    override func willBecomeActive(with conversation: MSConversation) {
        super.willBecomeActive(with: conversation)
        presentList()                      // まず一覧を見せる
    }
 
    func didSelectAsset(_ name: String) {
        // 選択されたら拡張表示へ広げて確認画面を出す
        requestPresentationStyle(.expanded)
        presentDetail(for: name)
    }
}

func send(asset name: String, in conversation: MSConversation) {
    let layout = MSMessageTemplateLayout()
    // 吹き出し用も原寸で読み込まない（後述の downsample を通す）
    layout.image = sharedAssetURL(name).flatMap {
        downsample($0, to: CGSize(width: 110, height: 238), scale: 3)
    }
    layout.caption = "お気に入りの一枚を送りました"
 
    let message = MSMessage()
    message.layout = layout
    conversation.insert(message) { error in
        if let error = error {
            print("insert failed: \(error)")   // 送信枠への挿入失敗を握りつぶさない
        }
    }
}

// share-loop.mjs — Messages 拡張の共有ループを k で見る
const scenarios = [
  { name: '控えめ',   shareRate: 0.02, recipients: 1.0, openRate: 0.20, installRate: 0.15 },
  { name: '現実的',   shareRate: 0.05, recipients: 1.3, openRate: 0.30, installRate: 0.20 },
  { name: '強気',     shareRate: 0.12, recipients: 1.8, openRate: 0.40, installRate: 0.30 },
];
const seed = 1000;
 
for (const s of scenarios) {
  const k = s.shareRate * s.recipients * s.openRate * s.installRate;
  const mult = 1 / (1 - k);
  console.log(`${s.name} | k=${k.toFixed(4)} | ${mult.toFixed(3)}x | ${Math.round(seed * mult)}`);
}
 
const r = scenarios[1];                                  // 現実的シナリオの後段を固定して
const tail = r.recipients * r.openRate * r.installRate;  // k=0.5 に必要な共有率を逆算する
for (const target of [0.2, 0.5, 1.0]) {
  console.log(`k=${target} needs share rate ${((target / tail) * 100).toFixed(1)}%`);
}