---
title: "vImageBuffer_InitWithCGImage(_:_:_:_:_:)"
framework: accelerate
role: symbol
role_heading: Function
path: "accelerate/vimagebuffer_initwithcgimage(_:_:_:_:_:)"
---

# vImageBuffer_InitWithCGImage(_:_:_:_:_:)

Initializes a vImage buffer with the contents of a Core Graphics image.

## Declaration

```swift
func vImageBuffer_InitWithCGImage(_ buf: UnsafeMutablePointer<vImage_Buffer>, _ format: UnsafeMutablePointer<vImage_CGImageFormat>, _ backgroundColor: UnsafePointer<CGFloat>!, _ image: CGImage, _ flags: vImage_Flags) -> vImage_Error
```

## Parameters

- `buf`: The destination vImage buffer. On output, an initialized buffer with all fields populated.
- `format`: A doc://com.apple.accelerate/documentation/Accelerate/vImage_CGImageFormat structure. Pass an empty structure to specify that the function populates the format with the properties of the Core Graphics image. Pass a populated structure to specify that the function converts the Core Graphics image to the format.
- `backgroundColor`: If the source image contains alpha information and the format doesn’t contain alpha information, this function flattens the source image against this parameter.
- `image`: The source Core Graphics image.
- `flags`: The options to use when performing the operation. Pass doc://com.apple.accelerate/documentation/Accelerate/kvImageNoAllocate if the destination buffer references existing data; otherwise, pass doc://com.apple.accelerate/documentation/Accelerate/kvImageNoFlags.

## Mentioned in

Converting bitmap data between Core Graphics images and vImage buffers Optimizing image-processing performance

## Return Value

Return Value kvImageNoError; otherwise, one of the error codes in Data Types and Constants.

## Discussion

Discussion The following code shows a passthrough function that accepts a CGImage image, populates a vImage buffer from the image, and generates a CGImage image from the buffer. In this example, the call to vImageBuffer_InitWithCGImage(_:_:_:_:_:) populates the vImage_CGImageFormat and the vImage_Buffer variables with the properties of the source image: static func passThrough(sourceImage: CGImage) -> CGImage? {

var format = vImage_CGImageFormat()     var buffer = vImage_Buffer()          defer {         buffer.free()     }

vImageBuffer_InitWithCGImage(         &buffer,         &format,         nil,         sourceImage,         vImage_Flags(kvImageNoFlags))         // Perform image-processing operations on `buffer`.

let destinationCGImage = vImageCreateCGImageFromBuffer(         &buffer,         &format,         nil,         nil,         vImage_Flags(kvImageNoFlags),         nil)          return destinationCGImage?.takeRetainedValue() } Pass a fully initialized vImage_CGImageFormat to specify that vImageBuffer_InitWithCGImage(_:_:_:_:_:) converts the source CGImage image to the format that format describes. The following example converts the source image to a three-channel, 8-bit-per-channel RGB image: static func passThrough(sourceImage: CGImage) -> CGImage? {          var format = vImage_CGImageFormat(         bitsPerComponent: 8,         bitsPerPixel: 8 * 3,         colorSpace: CGColorSpaceCreateDeviceRGB(),         bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue),         renderingIntent: .defaultIntent)!

var buffer = vImage_Buffer()

defer {         buffer.free()     }          vImageBuffer_InitWithCGImage(         &buffer,         &format,         nil,         sourceImage,         vImage_Flags(kvImageNoFlags))          // Perform image-processing operations on RGB888 `buffer`.

let destinationCGImage = vImageCreateCGImageFromBuffer(         &buffer,         &format,         nil,         nil,         vImage_Flags(kvImageNoFlags),         nil)          return destinationCGImage?.takeRetainedValue() } important: If you provide a populated vImage_CGImageFormat with properties (such as bit-depth, color space, and channel ordering) that are different from those of the CGImage instance, vImage uses any-to-any conversion as part of the operation. If your app is latency-sensitive, provide either an empty vImage_CGImageFormat or a vImage_CGImageFormat with properties that match the source image to ensure that the operation avoids the conversion step.