# init(mutating:shape:) Creates a new `MLShapedArray` using a pixel buffer as the backing storage. ``` init(mutating pixelBuffer: CVPixelBuffer, shape: [Int]) ``` ## Parameters `pixelBuffer` The backing pixel buffer. It must be backed by `IOSurface`. `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 Use this initializer to create an `IOSurface` backed `MLShapedArray`, 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. ```swift 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 = MLShapedArray(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. ```swift var shapedArray = MLShapedArray(mutating: pixelBuffer, shape: [1]) shapedArray[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. ```swift var array1 = MLShapedArray(mutating: pixelBuffer, shape: [1]) array1[scalarAt: 0] = 0 // pixelBuffer is mutated. let array2 = array1 array1[scalarAt: 0] = 42 // Copy-on-Write assert(array1[scalarAt: 0] == 42) assert(array2[scalarAt: 0] == 0) ``` It is undefined behavior to mutate the pixel buffer directly without using `.withMutablePixelBufferIfAvailable`. --- 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)