ObjC->Swift - 使用vImage的高斯模糊

翻译自：http://www.jianshu.com/p/6dd0eab888a6 中使用vImage生成高斯模糊的图像。

class func boxBlurImage(image: UIImage, withBlurNumber blur: CGFloat) -> 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: UnsafeMutablePointer!
    
    // 从CGImage中获取数据
    let inProvider = CGImageGetDataProvider(img)
    let inBitmapData = CGDataProviderCopyData(inProvider)
    
    // 设置从CGImage获取对象的属性
    inBuffer.width = UInt(CGImageGetWidth(img))
    inBuffer.height = UInt(CGImageGetHeight(img))
    inBuffer.rowBytes = CGImageGetBytesPerRow(img)
    inBuffer.data = UnsafeMutablePointer(CFDataGetBytePtr(inBitmapData))
    pixelBuffer = malloc(CGImageGetBytesPerRow(img) * CGImageGetHeight(img))
    if pixelBuffer == nil {
        NSLog("No pixel buffer!")
    }
    
    outBuffer.data = pixelBuffer
    outBuffer.width = UInt(CGImageGetWidth(img))
    outBuffer.height = UInt(CGImageGetHeight(img))
    outBuffer.rowBytes = CGImageGetBytesPerRow(img)
    
    error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer, nil, 0, 0, UInt32(boxSize), UInt32(boxSize), nil, UInt32(kvImageEdgeExtend))
    if error != nil && error != 0 {
        NSLog("error from convolution %ld", error)
    }
    
    let colorSpace = CGColorSpaceCreateDeviceRGB()
    let ctx = CGBitmapContextCreate(outBuffer.data, Int(outBuffer.width), Int(outBuffer.height), 8, outBuffer.rowBytes, colorSpace, CGImageAlphaInfo.NoneSkipLast.rawValue)
    
    let imageRef = CGBitmapContextCreateImage(ctx)!
    let returnImage = UIImage(CGImage: imageRef)
    
    free(pixelBuffer)

    return returnImage
}