Question

我正在使用AlamofireImage从我的CDN下载图像，但我想将自定义过滤器（灰度）应用于下载的某些图像。目前我使用scrollView显示所有可用图像，如果图像具有特定属性，请应用过滤器。

我是AlamofireImage的新手，所以我不知道如何应用自定义过滤器。

我申请了

reloadData

到filter参数，所以我知道实际的过滤器进程正在运行，但有人可以帮助创建自定义过滤器以将灰度应用于下载的图像吗？

Answer 1

方法＃1

使用Alamofireimage＆＃34; imageWithAppliedCoreImageFilter＆＃34; UIImage扩展。但由于某些原因，他们没有提供简单的协议访问此过滤器选项，所以让我们创建一个......

public struct CoreImageFilter: ImageFilter {

    let filterName: String
    let parameters: [String: AnyObject]

    public init(filterName : String, parameters : [String : AnyObject]?) {
        self.filterName = filterName
        self.parameters = parameters ?? [:]
    }

    public var filter: UIImage -> UIImage {
        return { image in
            return image.af_imageWithAppliedCoreImageFilter(self.filterName, parameters: self.parameters) ?? image
    }
}

Alamofireimage用户应该熟悉用法：

let imageView = UIImageView(frame: frame)
let URL = NSURL(string: "https://httpbin.org/image/png")!
let placeholderImage = UIImage(named: "placeholder")!
let color = CIColor(color: UIColor.grayColor())  // or whatever color desired
let intensity = 1.0  // 1.0 is the default, but setting it manually here to allow adjustment
let filter = CoreImageFilter(filterName: "CIColorMonochrome", parameters: ["inputColor": color, "inputIntensity" : intensity])

imageView.af_setImageWithURL(
    URL,
    placeholderImage: placeholderImage,
    filter: filter
)

如果你对CIColorMonochrome滤镜不满意（我不是），这里有一些其他的选择......

let filter = CoreImageFilter(filterName: "CIPhotoEffectTonal", parameters: nil)

或

let filter = CoreImageFilter(filterName: "CIPhotoEffectNoir", parameters: nil)

这是Apple开发网站上complete list of available filters的链接。

方法＃2

查找自定义过滤条件，例如What is the best Core Image filter to produce black and white effects?的评分最高的答案。

然后创建一个扩展名。对于以下代码正文，请Shmidt和DerGote。

extension UIImage {
    public func ff_imageFilteredToGrayScale() -> UIImage? {
        let context = CIContext(options: nil)
        let ciImage = CoreImage.CIImage(image: self)!

        // Set image color to b/w
        let bwFilter = CIFilter(name: "CIColorControls")!
        bwFilter.setValuesForKeysWithDictionary([kCIInputImageKey:ciImage, kCIInputBrightnessKey:NSNumber(float: 0.0), kCIInputContrastKey:NSNumber(float: 1.1), kCIInputSaturationKey:NSNumber(float: 0.0)])
        let bwFilterOutput = (bwFilter.outputImage)!

        // Adjust exposure
        let exposureFilter = CIFilter(name: "CIExposureAdjust")!
        exposureFilter.setValuesForKeysWithDictionary([kCIInputImageKey:bwFilterOutput, kCIInputEVKey:NSNumber(float: 0.7)])
        let exposureFilterOutput = (exposureFilter.outputImage)!

        // Create UIImage from context
        let bwCGIImage = context.createCGImage(exposureFilterOutput, fromRect: ciImage.extent)
        let resultImage = UIImage(CGImage: bwCGIImage, scale: 1.0, orientation: self.imageOrientation)

        return resultImage
    }
}

和结构......

public struct GrayScaleFilter: ImageFilter {

    public init() {
    }

    public var filter: UIImage -> UIImage {
        return { image in
            return image.ff_imageFilteredToGrayScale() ?? image
        }
    }
}

最后，用法......

let imageView = UIImageView(frame: frame)
let URL = NSURL(string: "https://httpbin.org/image/png")!
let placeholderImage = UIImage(named: "placeholder")!

let filter = GrayScaleFilter()

imageView.af_setImageWithURL(
    URL,
    placeholderImage: placeholderImage,
    filter: filter
)

如何应用自定义过滤器

1 个答案: