使用 vImage 生成高斯模糊图像，ObjC -> Swift 4，翻译自 iOS开发探索-高斯模糊&毛玻璃效果。

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private func vBlurImage(_ image: UIImage, blurNumber blur: Float) -> UIImage {
    var blur = blur
    if blur < 0.0 || blur > 1.0 {
        blur = 0.5
    }
    var boxSize = Int(blur * 40)
    boxSize = boxSize - (boxSize % 2) + 1
    
    let img = image.cgImage!
    
    var inBuffer = vImage_Buffer()
    var outBuffer = vImage_Buffer()
    var error: vImage_Error!
    var pixelBuffer: UnsafeMutableRawPointer?
    
    // 从CGImage中获取数据
    let inProvider = img.dataProvider!
    let inBitmapData = inProvider.data!
    
    // 设置从CGImage获取对象的属性
    inBuffer.width = UInt(img.width)
    inBuffer.height = UInt(img.height)
    inBuffer.rowBytes = img.bytesPerRow
    inBuffer.data = UnsafeMutableRawPointer(mutating: CFDataGetBytePtr(inBitmapData))
    pixelBuffer = malloc(img.bytesPerRow * img.height)
    if pixelBuffer == nil {
        print("No pixel buffer!")
    }
    
    outBuffer.data = pixelBuffer
    outBuffer.width = UInt(img.width)
    outBuffer.height = UInt(img.height)
    outBuffer.rowBytes = img.bytesPerRow
    
    error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer, nil, 0, 0, UInt32(boxSize), UInt32(boxSize), nil, UInt32(kvImageEdgeExtend))
    if error != nil && error != 0 {
        print("error from convolution \(error)")
    }
    
    let colorSpace = CGColorSpaceCreateDeviceRGB()
    let ctx = CGContext(data: outBuffer.data, width: Int(outBuffer.width), height: Int(outBuffer.height), bitsPerComponent: 8, bytesPerRow: outBuffer.rowBytes, space: colorSpace, bitmapInfo: CGImageAlphaInfo.noneSkipLast.rawValue)
    
    let imageRef = ctx!.makeImage()!
    let returnImage = UIImage(cgImage: imageRef)
    
    return(pixelBuffer)
    
    return returnImage
}

参考