---
title: "init(mutating:shape:)"
framework: coreml
role: symbol
role_heading: Initializer
path: "coreml/mlshapedarrayslice/init(mutating:shape:)"
---

# init(mutating:shape:)

Creates a new MLShapedArraySlice using a pixel buffer as the backing storage.

## Declaration

```swift
init(mutating pixelBuffer: CVPixelBuffer, shape: [Int])
```

## Parameters

- `pixelBuffer`: The pixel buffer to be owned by the instance.
- `shape`: The shape of the MLShapedArray. The last dimension of shape must match the pixel buffer’s width. The product of the rest of the dimensions must match the height.

## Discussion

Discussion Use this initializer to create an IOSurface backed MLShapedArraySlice, which can reduce the inference latency by avoiding the buffer copy. The pixel buffer’s pixel format type must be OneComponent16Half for scalar type Float16 and OneComponent8 for scalar type Int8. Other data types are not supported. var pixelBuffer: CVPixelBuffer? let pixelBufferAttributes = [     kCVPixelBufferIOSurfacePropertiesKey : [:] ] // Pixel buffer's width is the last dimension of `shape`, which is 4. // The height is the product of the rest of the dimensions, which is // 2 * 3 = 6. CVPixelBufferCreate(kCFAllocatorDefault,                     4, 6,                     kCVPixelFormatType_OneComponent16Half,                     pixelBufferAttributes as CFDictionary,                     &pixelBuffer)

let shapedArray = MLShapedArraySlice<Float16>(mutating: pixelBuffer!,                                               shape: [2, 3, 4]) When there is one and only one owner of the shaped array, mutating operations modifies the underlying pixel buffer. var slice = MLShapedArraySlice<Float16>(mutating: pixelBuffer, shape: [1]) slice[scalarAt: 0] = 42 // The pixel buffer now has 42 in its frame buffer. It follows the value semantics. The mutation doesn’t affect the copy. var slice1 = MLShapedArraySlice<Float16>(mutating: pixelBuffer, shape: [1]) slice1[scalarAt: 0] = 0 // pixelBuffer is mutated. let slice2 = slice1 slice1[scalarAt: 0] = 42 // Copy-on-Write

assert(slice1[scalarAt: 0] == 42) assert(slice2[scalarAt: 0] == 0)

## See Also

### Creating a shaped array slice

- [init(scalar:)](coreml/mlshapedarrayslice/init(scalar:).md)
- [init(scalars:shape:)](coreml/mlshapedarrayslice/init(scalars:shape:).md)