Android Compose：在图像上绘制透明圆圈

I have an image and I want to draw dark rectangle over it with a transparent circle, so the result will be something like this:

我最终得到了这段代码：

Box(modifier = Modifier
        .clip(RectangleShape)
        .fillMaxSize()
        .background(Color.Black)
        .pointerInput(Unit) {
            detectTransformGestures { centroid, pan, zoom, rotation ->
                scale *= zoom
            }
        }) {
        Image(
            modifier = Modifier
                .align(Alignment.Center)
                .graphicsLayer(
                    scaleX = maxOf(.2f, minOf(5f, scale)),
                    scaleY = maxOf(.2f, minOf(5f, scale))
                ),
            bitmap = bitmap.asImageBitmap(),
            contentDescription = null
        )
        Canvas(modifier = Modifier.fillMaxSize(), onDraw = {
            drawRect(Color.Black.copy(alpha = 0.8f))
            drawCircle(
                Color.Transparent,
                style = Fill,
                blendMode = BlendMode.Clear
            )
        })
    }

但它似乎只是在图像顶部画了一个黑圆圈，而不是清除变暗的矩形......

如果您建议如何根据此圆坐标裁剪图像，这也会非常方便。

你需要使用clipPath在这种情况下。

Canvas(modifier = Modifier.fillMaxSize(), onDraw = {
    val circlePath = Path().apply {
        addOval(Rect(center, size.minDimension / 2))
    }
    clipPath(circlePath, clipOp = ClipOp.Difference) {
        drawRect(SolidColor(Color.Black.copy(alpha = 0.8f)))
    }
})