# multiply(by:preBias:postBias:destination:) Multiplies each four channel pixel in a 32-bit-per channel, 4-channel pixel buffer by a 4 x 4 matrix to produce a four channel result. ``` func multiply(by matrix: Matrix, preBias: (Float, Float, Float, Float), postBias: (Float, Float, Float, Float), destination: vImage.PixelBuffer) where Matrix : AccelerateBuffer, Matrix.Element == Float ``` ## Parameters `matrix` The 4 x 4 multiplication matrix values in row-major order. `preBias` Values that the function adds to the source before multiplication. `postBias` A value that the function adds to the result after multiplication. `destination` The destination pixel buffer. ## Discussion This function applies the following operation to each pixel: ```swift p = (source.0 + preBias.0) * matrix.0 + (source.1 + preBias.1) * matrix.1 + (source.2 + preBias.2) * matrix.2 + (source.3 + preBias.3) * matrix.3 destination = (p + postBias) ``` --- 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)