# decode The decode array for the image. ``` var decode: UnsafePointer! ``` ## Discussion The decode array contains the upper and lower bounds for each color channel. When you define a decode array, the conversion functions that accept a [`vImage_CGImageFormat`](/documentation/Accelerate/vImage_CGImageFormat) parameter apply a linear transform to map colors to the specified bounds. A decode array for an RGB color space contains six entries: one pair for each red, green, and blue channel. The following code shows how the vImage library remaps a buffer that contains five planar pixels in the range `0 ... 0.5` to the range `0 ... 1`. The code passes a decode array with the values `[0, 0.5]` to the [`makeCGImage(cgImageFormat:)`](/documentation/Accelerate/vImage/PixelBuffer/makeCGImage(cgImageFormat:)) function that remaps the source pixel values from `[0.0, 0.125, 0.25, 0.375, 0.5]` to `[0.0, 0.25, 0.5, 0.75, 1.0]`. ```swift // Create a grayscale vImage pixel buffer. let pixels: [Pixel_F] = [0.0, 0.125, 0.25, 0.375, 0.5] let pixelBuffer = vImage.PixelBuffer( pixelValues: pixels, size: .init(width: 5, height: 1), pixelFormat: vImage.PlanarF.self) // Define the decode array to `0 ... 0.5`. let decodeArray: [CGFloat] = [0, 0.5] decodeArray.withUnsafeBufferPointer { decodeArrayPtr in let cgImageFormat = vImage_CGImageFormat( bitsPerComponent: 32, bitsPerPixel: 32, colorSpace: Unmanaged.passRetained(CGColorSpaceCreateDeviceGray()), bitmapInfo: CGBitmapInfo( rawValue: CGBitmapInfo.byteOrder32Little.rawValue | CGBitmapInfo.floatComponents.rawValue | CGImageAlphaInfo.none.rawValue), version: 0, decode: decodeArrayPtr.baseAddress, renderingIntent: .defaultIntent) let cgImage = pixelBuffer.makeCGImage(cgImageFormat: cgImageFormat) // Display the raw pixel values of the `CGImage`. if let pixelData = cgImage?.dataProvider?.data { let pixelPointer = (pixelData as NSData) .bytes .assumingMemoryBound(to: Pixel_F.self) let recreatedPixels = UnsafeBufferPointer( start: pixelPointer, count: 5) // Prints "[0.0, 0.25, 0.5, 0.75, 1.0]". print(Array(recreatedPixels)) } } ``` Set the `decodeArray` to `nil` to prevent the vImage-Core Graphics conversion functions from remapping values. --- 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)