# unpremultiply(alpha:) Transforms a 32-bit planar pixel buffer in-place from premultiplied alpha format to nonpremultiplied alpha format. ``` func unpremultiply(alpha: vImage.PixelBuffer) ``` ## Parameters `alpha` An 32-bit planar pixel buffer that contains the alpha. ## Discussion This function divides the color values in `self` by the corresponding alpha values. For example, the following code premultiplies a 4 x 1 planar pixel buffer with the corresponding pixels in a separate planar alpha buffer: ```swift let src = vImage.PixelBuffer( pixelValues: [0.125, 0.25, 0.5, 1], size: vImage.Size(width: 4, height: 1)) let alpha = vImage.PixelBuffer( pixelValues: [0, 0.25, 0.5, 1], size: vImage.Size(width: 4, height: 1)) src.unpremultiply(alpha: alpha) // Prints "[0.0, ~1.0, ~1.0, ~1.0]". print(src.array) ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)