icon: flatten iOS app icons opaque (App Store 90717), keep Android transparent#37
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…ansparent Apple rejects any alpha channel on the App Store marketing icon (error 90717). write_ios_icons now flattens an alpha-bearing source onto an opaque background (explicit :background_color or the sampled adaptive-icon colour) before resizing; an opaque source is untouched. Android keeps transparency — adaptive foregrounds and legacy launcher icons need it, and a flat background looks bad on some launchers. mix mob.icon threads --adaptive-bg to both platforms. The bundled fallback mob_logo iOS assets (can't be flattened at runtime without the image dep) were pre-flattened opaque; Android-size assets keep their alpha. Verified on Sloppy Joe: the rebuilt IPA passed App Store validation to TestFlight. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Jul 8, 2026
iOS app icons are now flattened onto an opaque background so App Store upload validation no longer rejects a transparent source (altool error 90717). Android keeps its adaptive/legacy transparency. (#37) Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Problem
App Store upload validation rejects an app whose 1024 marketing icon has an alpha channel:
IconGenerator.write_ios_iconsjustImage.thumbnail!'d the source into each iOS size, so a transparent source (a common design — a rounded badge on transparent corners) produced transparent iOS icons and tripped 90717. The bundled fallbackmob_logoiOS assets had the same issue.Android must not be flattened — adaptive foregrounds + legacy launcher icons rely on transparency, and a flat background renders badly on some launchers. So the fix is platform-specific.
Fix
write_ios_iconsruns the source through a newflatten_for_ios/2: an alpha-bearing source is composited onto an opaque background viaImage.flatten!/2; an opaque source is left untouched.:background_coloroption, else sampled with the sameextract_background_color/1the adaptive Android background uses → the opaque iOS icon and the Android adaptive background share one colour.mix mob.iconthreads--adaptive-bgto both platforms.mob_logoiOS-size PNGs pre-flattened opaque (they can't be flattened at runtime without theimagedep). iOS/Android sizes are disjoint files, so Android assets keep their alpha.Tests
icon_generator_test.exs::background_colorfills the flattened iOS icon (asserts the centre pixel)Verified
Sloppy Joe (rounded-badge transparent icon): the rebuilt IPA passed App Store validation and reached TestFlight (this exact 90717 was how it was found).
ADR:
decisions/2026-07-08-ios-icons-flattened-opaque.md.🤖 Generated with Claude Code