# `GSShapeKey.GSShapeKeyOpacity`

*Type Property*

The key for the shape attribute value defining the alpha transparency (`-doubleValue` returning `double` in the range `0.0`, fully transparent, to `1.0`, fully opaque).

## Declaration

```swift
static let opacity: GSShapeKey
```

```objc
extern GSShapeKey const GSShapeKeyOpacity;
```

```python
GSShapeKeyOpacity: GSShapeKey
```