Make an app icon set from one square image

One 1024×1024 master becomes every iOS and Android size in a ZIP — opaque for iOS, transparency kept for Android.

Tools used in this guide

The job

App stores and build tools want your icon in a dozen exact sizes — 20pt through 1024px for iOS, mdpi through xxxhdpi for Android. Resizing a master by hand for each is the definition of a scriptable task.

Generate

Drop a square PNG (at least 512×512 — 1024 gives the sharpest results), pick iOS, Android, or both, and download a ZIP of every required size. iOS icons are flattened opaque since Apple rejects transparency; Android keeps your alpha.

Design to the safe zone: keep key art inside the middle 80% — launchers and stores mask the corners.
The ZIP contains only resized PNGs; wire the iOS Contents.json and Android mipmap folders yourself (names follow each platform's convention).

Worked example

A 1024×1024 logo exports as a 30-file ZIP: iOS 20–1024px (18 files, opaque) and Android 48–192px mipmaps plus a 512px Play Store icon (all keeping transparency).

Where it stops

Resizing only — it doesn't design the icon, add padding, or generate adaptive-icon foreground/background layers (Android adaptive needs a separate foreground). Source must be square, 512–8192 px, ≤ 32 MiB. The 64-file ZIP cap means it won't include icon sets for watchOS or other platforms.