[Android] 038. 画像のピンチイン/アウト

@Composable
fun TransformableImage() {
    val scaleMax = 5.0f
    var scale by remember { mutableStateOf(1.0f) }
    var offset by remember { mutableStateOf(Offset.Zero) }
    val state = rememberTransformableState { zoomChange, offsetChange, _ ->
        val scale_ = scale * zoomChange
        if (scale_ >= 1.0f && scale_ <= scaleMax) scale = scale_
        offset += Offset(offsetChange.x * scale, offsetChange.y * scale)
    }

    var animating by remember { mutableStateOf(false) }
    val zoom by animateFloatAsState(
        label = "",
        targetValue = if (scale <= scaleMax / 2) {
            if (animating) scaleMax else scale
        } else {
            if (animating) 1.0f else scale
        },
        animationSpec = tween(durationMillis = if (animating) 300 else 0),
        finishedListener = {
            if (animating) {
                animating = false
                scale = it
            }
        }
    )

    Box(
        Modifier
            .pointerInput(Unit) {
                detectTapGestures(
                    onPress = { /* Called when the gesture starts */ },
                    onDoubleTap = {
                        animating = true
                        offset = Offset.Zero
                    },
                    onLongPress = { /* Called on Long Press */ },
                    onTap = { /* Called on Tap */ }
                )
            }
            .graphicsLayer(
                scaleX = if (animating) zoom else scale,
                scaleY = if (animating) zoom else scale,
                translationX = offset.x,
                translationY = offset.y
            )
            .transformable(state = state)
            .background(Color.Blue)
            .fillMaxSize()
    ) {
        // <uses-permission android:name="android.permission.INTERNET" />
        val url = "https://..."
        Image(
            painter = rememberAsyncImagePainter(url), // io.coil-kt:coil-compose
            contentDescription = null,
            modifier = Modifier.fillMaxSize(),
            contentScale = ContentScale.FillWidth
        )
    }
}

var visible by remember { mutableStateOf(false) }
AnimatedVisibility(
    visible = visible,
    enter = slideInHorizontally(tween(50)) { width -> width },
    exit = slideOutHorizontally(tween(50)) { width -> width },
) {
...
}