---
title: unpremultiply()
framework: accelerate
role: symbol
role_heading: Instance Method
path: accelerate/vimage/pixelbuffer/unpremultiply()
---

# unpremultiply()

Transforms a floating-point 16-bit RGBA pixel buffer in-place from premultiplied alpha format to nonpremultiplied alpha format.

## Declaration

```swift
func unpremultiply()
```

## Discussion

Discussion This function divides the color values in each pixel self by the corresponding alpha value and copies the alpha value to the destination unchanged. For example, the following code divides the RGB values [0.125, 0.25, 0.5] by the alpha value 0.5: let pixelValues = [0.125, 0.25, 0.5,                    Float(0.5)].map {     return vImage.Planar16F.makePixel($0) }

let src = vImage.PixelBuffer<vImage.Interleaved16Fx4>(     pixelValues: pixelValues,     size: vImage.Size(width: 1, height: 1))      src.unpremultiply()

let result = src.array.map {     return vImage.PlanarF.makePixel($0) }

// Prints "[0.25, 0.5, 1.0, 0.5]". print(result)

## See Also

### Unpremultiply

- [unpremultiply(alpha:)](accelerate/vimage/pixelbuffer/unpremultiply(alpha:)-xnog.md)
- [unpremultiply(alpha:)](accelerate/vimage/pixelbuffer/unpremultiply(alpha:)-i0ri.md)
- [unpremultiply(channelOrdering:)](accelerate/vimage/pixelbuffer/unpremultiply(channelordering:)-1pkat.md)
- [unpremultiply(channelOrdering:)](accelerate/vimage/pixelbuffer/unpremultiply(channelordering:)-19l0s.md)
- [unpremultiply(channelOrdering:)](accelerate/vimage/pixelbuffer/unpremultiply(channelordering:)-82uq3.md)