---
title: decode
framework: accelerate
role: symbol
role_heading: Instance Property
path: accelerate/vimage_cgimageformat/decode
---

# decode

The decode array for the image.

## Declaration

```swift
var decode: UnsafePointer<CGFloat>!
```

## Discussion

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 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:) 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]. // 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<Pixel_F>(             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.

## See Also

### Instance properties

- [bitsPerComponent](accelerate/vimage_cgimageformat/bitspercomponent.md)
- [bitsPerPixel](accelerate/vimage_cgimageformat/bitsperpixel.md)
- [colorSpace](accelerate/vimage_cgimageformat/colorspace.md)
- [bitmapInfo](accelerate/vimage_cgimageformat/bitmapinfo.md)
- [version](accelerate/vimage_cgimageformat/version.md)
- [renderingIntent](accelerate/vimage_cgimageformat/renderingintent.md)
- [componentCount](accelerate/vimage_cgimageformat/componentcount.md)