Scratch Mechanic

Android sample app that implements a scratch-to-reveal card in Jetpack Compose: the user drags on a top “foil” layer; an image underneath appears through the scratched path. When enough of the visible area is covered, the overlay can fade out (“vanish”).

Demo

Screen_recording_20260413_183916.mp4

What’s in this project

• ScratchOverlay — Composable that stacks optional revealed content under scratchable content, handles drag gestures, draws the erase stroke with BlendMode.Clear on an offscreen layer, and runs the vanish animation.
• ScratchState — Holds the scratch polyline, grid-based coverage (no GPU pixel readback), optional clip via Android Region, and reveal flags.
• ScratchOverlayConfig / ScratchAreaSpec — Brush width, vanish threshold, animation duration, optional clipShape, and sizing (match scratchable vs fixed DpSize).

Requirements

• Android Studio / Gradle as in the project wrappers
• minSdk / compileSdk as defined in app/build.gradle.kts

Run

./gradlew :app:installDebug

Or open the project in Android Studio and run the app configuration.

License

Apache 2.0