Ios 使用CilanczosCaleTransform Core图像过滤器调整图像大小

我试图使用

CILanczosScaleTransform

核心图像过滤器调整图像大小，但遇到了问题。这是我的密码：

var imageView: UIImageView = UIImageView()
var image: UIImage?
imageView.frame = CGFrameMake(10,10,200,300)
dispatch_async(dispatch_get_main_queue(), {
    let nsurl = NSURL(string:"http://...")
    var err: NSError?
    var getImageData = NSData(contentsOfURL: nsurl!, options: NSDataReadingOptions.DataReadingMappedIfSafe, error: &err)
    if let imageData = getImageData {
        if let receivedImage = UIImage(data: imageData){
            image = receivedImage
/*
  so far all this code works fine, if I set imageView.image = image 
  the image displays with no problems...

  ...the problems are in this bit of code:
                                                    */
            let context = CIContext(options:nil)
            var ciimg = CIImage(image: image)
            var filter = CIFilter(name: "CILanczosScaleTransform")
            filter.setValue(image, forKey: kCIInputImageKey)
            filter.setValue(0.667, forKey: kCIInputScaleKey)
            let result: CIImage = filter.outputImage

            let extent = result.extent() // <-- specifically this line

            let newImage: UIImage? = UIImage(CIImage: result)
            imageView.image = newImage
        }
    }
})

我把我在Objective C上找到的代码翻译成了Swift，感觉可能是误译了

---

有人能纠正我的错误吗？

好的，这是我的错误。此行：

filter.setValue（image，forKey:kCIInputImageKey）

正在使用

image

中找到的

UIImage

并在过滤器内部使用它，而应该使用

ciimg

中找到的

CIImage

因此，完整的代码应该是：

var imageView: UIImageView = UIImageView()
var image: UIImage?
imageView.frame = CGFrameMake(10,10,200,300)
dispatch_async(dispatch_get_main_queue(), {
    let nsurl = NSURL(string:"http://...")
    var err: NSError?
    var getImageData = NSData(contentsOfURL: nsurl!, options: NSDataReadingOptions.DataReadingMappedIfSafe, error: &err)
    if let imageData = getImageData {
        if let receivedImage = UIImage(data: imageData){
            image = receivedImage
            let context = CIContext(options:nil)
            var ciimg = CIImage(image: image)
            var filter = CIFilter(name: "CILanczosScaleTransform")
            filter.setValue(ciimg, forKey: kCIInputImageKey)
            filter.setValue(0.667, forKey: kCIInputScaleKey)
            let result: CIImage = filter.outputImage
            let extent = result.extent()
            let newImage: UIImage? = UIImage(CIImage: result)
            imageView.image = newImage
        }
    }
})

---

除了CGFrameMake之外，代码对我来说很好，但那是无关紧要的。

var imageView: UIImageView = UIImageView()
var image: UIImage?
imageView.frame = CGFrameMake(10,10,200,300)
dispatch_async(dispatch_get_main_queue(), {
    let nsurl = NSURL(string:"http://...")
    var err: NSError?
    var getImageData = NSData(contentsOfURL: nsurl!, options: NSDataReadingOptions.DataReadingMappedIfSafe, error: &err)
    if let imageData = getImageData {
        if let receivedImage = UIImage(data: imageData){
            image = receivedImage
            let context = CIContext(options:nil)
            var ciimg = CIImage(image: image)
            var filter = CIFilter(name: "CILanczosScaleTransform")
            filter.setValue(ciimg, forKey: kCIInputImageKey)
            filter.setValue(0.667, forKey: kCIInputScaleKey)
            let result: CIImage = filter.outputImage
            let extent = result.extent()
            let newImage: UIImage? = UIImage(CIImage: result)
            imageView.image = newImage
        }
    }
})