CoreML style transfer with Vision (workaround while VNPixelBufferObservation.pixelBuffer is broken)

StyleTransfer.swift

import Foundation
import UIKit
import CoreML
import Vision

// Quick and dirty example of how to fix Vision VNPixelBufferObservation BAD_ACCESS.
// Please handle errors in swift by yourself, this code sample intended only for demonstration.
// MLModel must have multiArray output and Image input.
// Before using this functions install CoreMLHelpers from https://github.com/hollance/CoreMLHelpers

func deprocessArray(_ array: MLMultiArray) -> MLMultiArray {
    let bias = [103.939, 116.779, 123.68]
    var arr = MultiArray<Double>(array)
    for h in 0..<arr.shape[1] {
        for w in 0..<arr.shape[2] {
            // Add bias
            let b = arr[0, h, w] + bias[0]
            let g = arr[1, h, w] + bias[1]
            let r = arr[2, h, w] + bias[2]
            
            // BGR -> RGB
            arr[0, h, w] = r
            arr[1, h, w] = g
            arr[2, h, w] = b
        }
    }
    return arr.array
}

func stylize(cgImage: CGImage) -> CGImage {
    let model = try! VNCoreMLModel(for: feathers_array().model)
    let request = VNCoreMLRequest(model: model)
    let handler = VNImageRequestHandler(cgImage: cgImage, options: [:])
    try! handler.perform([request])
    
    let result = request.results![0] as! VNCoreMLFeatureValueObservation
    let array = deprocessArray(result.featureValue.multiArrayValue!)
    let img = array.image(offset: 0.0, scale: 1.0)!
    return img.cgImage!
}