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# sourceAlpha

Premultiplication description for the source texture.

```
var sourceAlpha: MPSAlphaType { get }
```

## Discussion

Most color space conversion operations can not work directly on premultiplied data. Use this property to tag premultiplied data so that the source texture can be un-premultiplied prior to the application of these transforms. The default value is [`MPSAlphaType.alphaIsOne`](/documentation/MetalPerformanceShaders/MPSAlphaType/alphaIsOne).

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