Dev App Assets

App assets

A one-shot pipeline that turns a single app idea into the full store-ready asset pack: app icon across every required size, splash screen, device-framed App Store / Play Store screenshots, and feature graphic. One visual language, one style reference, every platform.

When to Use

• Launching an iOS / Android / cross-platform app and need the full asset set before submission.
• Rebranding an existing app: re-render all icons + store art in a new style.
• Indie / hackathon ships where you'd otherwise hand-crop 30 icon sizes.
• Watch + phone + tablet variants that must feel like one product.
• Regenerating localized App Store screenshots for new markets.

Not for: motion assets (use gen-ai-use), marketing LP heroes (dev-screenshot-beautifier), or final pixel-perfect logo work (hand off to a designer).

Prerequisites

Ask before generating (one message, 6 questions):

1. App name + one-line concept (e.g. "Rally — a focus timer for ADHD brains").
2. Style direction: flat, gradient, claymorphic, glass, pixel? Any existing logo or style exemplar to reference?
3. Brand tokens: primary + accent colors (hex), typography, mood keywords.
4. Platforms: iOS, Android, watchOS, macOS, web PWA — which sizes do you need?
5. Device frames for screenshots: iPhone 16 Pro, Pixel 9, Apple Watch, iPad Pro? Portrait or landscape?
6. Deliverable folder: where should the pack land (e.g. ./app-assets/)?

How to Run

1. Estimate + validate the master style.

   gen-ai models info flux-2-pro
   gen-ai generate -m flux-2-pro -p "<style prompt>" --aspect-ratio 1:1 --dry-run --debug
   

2. Generate the master icon (1024×1024, the source-of-truth). This is what every downstream size gets derived from — make it right once.

   gen-ai generate -m flux-2-pro \
     -p "app icon, 'Rally' focus timer, minimalist gradient, magenta #FF006E to purple #8338EC, soft shadow, rounded-rect canvas, centered glyph, hyperreal studio render" \
     --aspect-ratio 1:1 \
     --download ./app-assets/icon-master \
     --save-to-drive --drive-folder "rally-app-assets"
   

   Review visually. Regenerate until approved — do NOT batch before the master is locked.

3. Derive all icon sizes locally (no gen-ai credits). Icons are deterministic resizes of the master.

   MASTER=./app-assets/icon-master/result.png
   # iOS sizes (App Store 1024, iPhone 60@2x/@3x, iPad, Settings, Spotlight, Notification)
   for size in 1024 180 120 167 152 76 87 80 58 40 120 87 58; do
     sips -z $size $size "$MASTER" --out "./app-assets/ios/icon-${size}.png"
   done
   # Android (mipmap-mdpi … xxxhdpi: 48, 72, 96, 144, 192, 512)
   for size in 48 72 96 144 192 512; do
     sips -z $size $size "$MASTER" --out "./app-assets/android/ic_launcher-${size}.png"
   done
   # watchOS (24, 27.5, 29, 40, 44, 50, 86, 98, 108)
   for size in 48 55 58 80 88 100 172 196 216; do
     sips -z $size $size "$MASTER" --out "./app-assets/watch/icon-${size}.png"
   done
   

4. Generate the splash / launch screen off the same master (keep visual DNA).

   gen-ai generate -m flux-kontext-pro \
     -i ./app-assets/icon-master/result.png \
     -p "splash screen, centered app icon on a vertical gradient, same magenta-to-purple palette, 9:19.5 mobile canvas, calm negative space" \
     --aspect-ratio 9:16 \
     --download ./app-assets/splash
   

5. Batch the App Store screenshots — one manifest per platform, framed separately.

   gen-ai batch run app-store-shots.json -c 4 -o ./app-assets/screenshots
   

   Then wrap with device frames using dev-screenshot-beautifier (see that skill) or a tool like fastlane frameit.

6. Feature graphic (Play Store) + promo (App Store).

   gen-ai generate -m flux-2-pro \
     -p "Play Store feature graphic, 'Rally' wordmark, 1024×500, same gradient, key benefit 'Focus in bursts'" \
     --aspect-ratio 1024x500 \
     --download ./app-assets/store
   

7. Verify mask alignment. iOS auto-masks to a rounded-rect; content must sit inside the safe zone or you'll get clipped corners. Preview at 60×60 — if the glyph bleeds, regenerate with centered glyph, 15% padding all sides in the prompt.

Quick Reference

App Store screenshots (6.9" iPhone, 1290×2796, 5 screens):

{
  "defaults": {
    "model": "flux-kontext-pro",
    "aspectRatio": "1290x2796",
    "imageUrls": ["./app-assets/icon-master/result.png"]
  },
  "jobs": [
    { "id": "screen-1-hero",      "prompt": "iPhone app UI mockup, 'Rally' focus timer home screen, large timer dial, magenta-to-purple gradient, tagline 'Focus in bursts' above the fold" },
    { "id": "screen-2-session",   "prompt": "iPhone app UI mockup, active focus session, glowing timer ring at 00:14:23, calm dark background" },
    { "id": "screen-3-stats",     "prompt": "iPhone app UI mockup, weekly focus stats bar chart, magenta bars, caption 'You focused 12h this week'" },
    { "id": "screen-4-streak",    "prompt": "iPhone app UI mockup, 14-day streak celebration, confetti, flame icon, headline 'Day 14 unlocked'" },
    { "id": "screen-5-settings",  "prompt": "iPhone app UI mockup, settings screen, clean list rows, same palette, tagline 'Built for ADHD brains'" }
  ]
}

Quick Reference

Confirm IDs with gen-ai models --mode image.

Procedure

• Lock the master before batching. One great 1024 is worth 30 mediocre variants. Never run the icon-size loop until the master is approved.
• Resize locally, don't regenerate. sips / ImageMagick / sharp for all sizes below the master. AI-regenerating each size produces drift.
• Reference the master for every downstream asset. -i icon-master.png into splash, screenshots, feature graphic. Shared visual DNA.
• Respect iOS mask. iOS auto-clips to a superellipse at the OS level; keep the glyph within 80% of the canvas, centered. Test at 60×60 before committing.
• Android adaptive icons need separate foreground + background layers (108×108 with 72×72 safe zone). Generate foreground transparent, background as a solid/gradient tile.
• Save everything to Drive. --drive-folder "<app>-assets" — so a designer can review in one place without cloning your repo.
• Version the style prompt. Store the exact prompt in app-assets/STYLE.md. Future "just one more screenshot" requests stay consistent.
• Don't re-render on every CI run. Assets are release artifacts — commit them, or generate once and upload to your asset pipeline.

Pitfalls

Verification

Run gen-ai whoami to confirm authentication, then re-run the failed command with --debug.

Cost & time

See also

• gen-ai-use.md — CLI reference, flags, auth
• gen-ai-batch.md — manifest shapes, batch resume, concurrency tuning
• gen-ai-workflows.md — Workflow 5 (launch kit) for motion/reel companion assets
• dev-screenshot-beautifier — device-frame the App Store screenshots
• dev-og-image-service — social cards for the marketing site