ios-app-icon-asset-prep

name	ios-app-icon-asset-prep
description	MANDATORY when adding or updating icons in AppIcon.appiconset/. Enforces 1024x1024 sizing and the per-variant alpha rules (primary opaque, dark transparent, tinted opaque grayscale).

iOS App Icon Asset Prep

RULES — Follow these with no exceptions

1. The icon must be exactly 1024x1024 px. Not 1023, not 1025, not 1024x1200 cropped. App Store Connect rejects uploads with dimensions off by a single pixel.
2. No alpha channel on the primary (light) icon. RGB only — it doubles as the App Store marketing icon, and an alpha channel (even fully opaque) triggers ITMS-90717 "Invalid App Store Icon" on upload. This rule applies ONLY to the primary icon: the dark variant is supposed to have a transparent background, and the tinted variant should be opaque grayscale.
3. Flatten the primary icon onto a solid background before saving. A transparent-looking-opaque PNG still carries an alpha channel. Use scripts/strip-alpha-from-icon.sh — it flattens via ImageMagick (lossless) with an sips JPEG round-trip fallback. Do NOT flatten the dark variant.
4. Provide both light and dark variants in Contents.json using appearances: [{ appearance: luminosity, value: dark }]. Dark mode is required for a polished iOS 17+ app. Per Apple's docs, give the dark icon a transparent background so the system-provided dark background shows through.
5. No text, no tagline, no version number. Apple's icon guidelines reject icons with more than a logomark. Save the text for the Marketing Screenshot.
6. The pre-archive validator blocks archive if an alpha channel is detected on primary icons under AppIcon.appiconset/ (files named *dark* / *tinted* are exempt).

---

When to invoke

• Dropping a new icon PNG into Assets.xcassets/AppIcon.appiconset/.
• Replacing the existing icon.
• Adding a dark-mode or tinted variant.
• Debugging "Invalid Icon" uploads to App Store Connect.

The 1024×1024 / RGB / no-alpha rule

A classic App Store rejection looks like:

ERROR ITMS-90717: "Invalid App Store Icon. The App Store Icon in the asset catalog
in 'YourApp.app' can't be transparent or contain an alpha channel."

This happens because iOS asset catalogs were designed for UI images (which often want alpha), but the App Store binary-checker singles out the 1024×1024 marketing icon — i.e. the primary/light variant — and demands opaque RGB.

Detect:

sips -g hasAlpha icon-1024.png
#   pixelHeight: 1024
#   pixelWidth: 1024
#   hasAlpha: yes     ← will be rejected

Auto-fix: invoke scripts/strip-alpha-from-icon.sh <path>:

# Uses ImageMagick when available, else sips JPEG round-trip
bash "${CLAUDE_PLUGIN_ROOT}/scripts/strip-alpha-from-icon.sh" \
  YourApp/Assets.xcassets/AppIcon.appiconset/icon-1024.png

# Background color override (default: FFFFFF)
ICON_BG=000000 bash "${CLAUDE_PLUGIN_ROOT}/scripts/strip-alpha-from-icon.sh" \
  path/to/icon.png

The script reads the PNG, flattens it onto a solid-color background, and writes it back in place. Ask the user which background color matches the icon's intended surround (typically the edge color of the icon or pure white/black).

Light + dark variants via Contents.json

iOS 17+ supports a dark-mode icon variant that kicks in when the user has Dark Mode enabled and the icon is rendered over dark wallpaper in the lock-screen / widget contexts. The asset catalog declares it:

{
  "images": [
    {
      "idiom": "universal",
      "platform": "ios",
      "size": "1024x1024",
      "filename": "icon-1024.png"
    },
    {
      "appearances": [
        { "appearance": "luminosity", "value": "dark" }
      ],
      "idiom": "universal",
      "platform": "ios",
      "size": "1024x1024",
      "filename": "icon-1024-dark.png"
    }
  ],
  "info": { "author": "xcode", "version": 1 }
}

See <plugin-root>/templates/AppIcon-Contents.json.template — drop into Assets.xcassets/AppIcon.appiconset/Contents.json verbatim and supply the two PNGs (icon-1024.png for light, icon-1024-dark.png for dark).

Both variants must be 1024×1024 sRGB PNGs. The no-alpha rule applies only to the light icon — the dark variant keeps its transparent background (Apple: "Provide your dark app icon with a transparent background so the system-provided background can show through").

Tinted variant (iOS 18+, optional)

iOS 18 added a tinted appearance — the system recolors the icon to match the user's Home Screen tint. If you want to support it:

{
  "appearances": [
    { "appearance": "luminosity", "value": "tinted" }
  ],
  "idiom": "universal",
  "platform": "ios",
  "size": "1024x1024",
  "filename": "icon-1024-tinted.png"
}

Tinted icon rules:

• Grayscale only; the system supplies the background and applies the tint.
• Fully opaque, and encoded as RGB with grayscale values — a Gray Gamma colorspace PNG triggers an App Store Connect icon-display bug. Keep all variants the same format (PNG).
• High-contrast — thin line work gets lost.

This variant is optional. If omitted, iOS auto-generates a tinted version from the light variant, which usually looks worse than a hand-crafted one.

Pre-archive validator enforcement

scripts/validate_pre_archive.sh Check 3 walks the PNGs under AppIcon.appiconset/ — skipping *dark* / *tinted* filenames, which are allowed (dark) or not required (tinted) to carry alpha — and runs:

sips -g hasAlpha "$icon" | grep -q "hasAlpha: yes"

If alpha is detected, the validator fails with exit code 2 and prints the remediation command:

🚫 Pre-archive validation FAILED:
   • App icon has alpha channel: ./YourApp/Assets.xcassets/AppIcon.appiconset/icon-1024.png.
     Run: bash ${CLAUDE_PLUGIN_ROOT}/scripts/strip-alpha-from-icon.sh '<path>'

The validator runs before xcodebuild archive, catching the issue ~90 seconds before the archive step would have discovered it.

Escape hatch (rare): IOS_FROM_WEB_SKIP_VALIDATOR=1 — document why in the commit message.

Common pitfalls

"I exported from Figma as PNG — why is there alpha?"

Figma / Sketch / Photoshop default to RGBA. Even a fully opaque canvas carries an alpha channel.

Fix: run strip-alpha-from-icon.sh after export, or configure Figma to "Export as JPEG then convert to PNG" (avoids alpha entirely).

"My icon looks fine in Xcode but the upload fails"

Xcode's asset catalog viewer silently ignores alpha. App Store Connect doesn't.

Fix: always check sips -g hasAlpha <path> before uploading, or let the pre-archive validator do it.

"1024x1024 but App Store still rejects"

Cause: color profile is CMYK (common from Illustrator exports). App Store requires sRGB.

Fix: sips -s format png -s formatOptions normal --setProperty colorProfile "sRGB IEC61966-2.1" in.png --out out.png.

"Dark variant doesn't activate"

Cause: Contents.json has the wrong appearance key, or the PNG was swapped but the filename in Contents.json doesn't match.

Fix: filenames must match Contents.json exactly. Use the template from <plugin-root>/templates/AppIcon-Contents.json.template.

"Tinted variant looks muddy"

Cause: exported from color art and the contrast collapses under tint.

Fix: re-export as high-contrast, fully opaque grayscale (encoded as RGB). The system supplies the background and does the tinting at runtime.

Template reference

• <plugin-root>/templates/AppIcon-Contents.json.template — drop-in Contents.json with light + dark variants.
• <plugin-root>/scripts/strip-alpha-from-icon.sh — one-shot alpha stripper.

Related skills

• ios-project-structure — where Assets.xcassets lives and how the target references it.
• ios-info-plist-privacy-strings — the other common pre-archive blocker.