This is an accelerate based conversion for macOS but maybe it will help you along: func normaliseImage(inImage: CGImage?) -> CGImage? { guard let cgImage = inImage ?? originalnsimage.cgImage(forProposedRect: nil, context: nil, hints: nil) else {return nil} guard let format = vImage_CGImageFormat(cgImage: cgImage) else {return nil} guard let sourceBuffer = try? vImage_Buffer(cgImage: cgImage, format: format) else {return nil} defer {sourceBuffer.free()} bitsperPixel = min(cgImage.bitsPerPixel, 32) bitsperComponent = min(cgImage.bitsPerComponent, 8) // Get workable argb image format in return let argbFormat: vImage_CGImageFormat = { return vImage_CGImageFormat(bitsPerComponent: bitsperComponent, bitsPerPixel: bitsperPixel, colorSpace: originalColorSpace, bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.first.rawValue), renderingIntent: .defaultIntent)! }() guard var destinationBuffer = try? vImage_Buffer(width: Int(sourceBuffer.width), height: Int(sourceBuffer.height), bitsPerPixel: argbFormat.bitsPerPixel) else {return nil} defer {destinationBuffer.free()} if let toRgbConverter = try? vImageConverter.make(sourceFormat: format, destinationFormat: argbFormat) { try? toRgbConverter.convert(source: sourceBuffer, destination: &destinationBuffer) } let result = try? destinationBuffer.createCGImage(format: argbFormat) return result }