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# opaque

A Boolean value that indicates whether the underlying Core Graphics context has an alpha channel.

```
var opaque: Bool { get set }
```

## Discussion

Setting the value of this property to <doc://com.apple.documentation/documentation/Swift/false> specifies that the underlying Core Graphics context has an alpha channel, whereas <doc://com.apple.documentation/documentation/Swift/true> indicates it does not. The default value is <doc://com.apple.documentation/documentation/Swift/false>.

A Core Graphics context requires an alpha channel to express transparency. Without an alpha channel a Core Graphics context is said to be opaque, i.e. without transparency.

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