一、Core Image是和啥？
关于这个问题不太好回答，但其实又也很简单。肯定是苹果推出的关于图片处理的API。网上各路大神都有解释过，不过能看明白的不多，我的理解就是Photoshop的滤镜，当然在各种美图软件里都有这个功能，咱主要看怎么用吧
二、Core Image提供了哪些可用的滤镜呢？
127 values { [0] = "CIAccordionFoldTransition" [1] = "CIAdditionCompositing" [2] = "CIAffineClamp" [3] = "CIAffineTile" [4] = "CIAffineTransform" [5] = "CIAreaHistogram" [6] = "CIAztecCodeGenerator" [7] = "CIBarsSwipeTransition" [8] = "CIBlendWithAlphaMask" [9] = "CIBlendWithMask" [10] = "CIBloom" [11] = "CIBumpDistortion" [12] = "CIBumpDistortionLinear" [13] = "CICheckerboardGenerator" [14] = "CICircleSplashDistortion" [15] = "CICircularScreen" [16] = "CICode128BarcodeGenerator" [17] = "CIColorBlendMode" [18] = "CIColorBurnBlendMode" [19] = "CIColorClamp" [20] = "CIColorControls" [21] = "CIColorCrossPolynomial" [22] = "CIColorCube" [23] = "CIColorCubeWithColorSpace" [24] = "CIColorDodgeBlendMode" [25] = "CIColorInvert" [26] = "CIColorMap" [27] = "CIColorMatrix" [28] = "CIColorMonochrome" [29] = "CIColorPolynomial" [30] = "CIColorPosterize" [31] = "CIConstantColorGenerator" [32] = "CIConvolution3X3" [33] = "CIConvolution5X5" [34] = "CIConvolution9Horizontal" [35] = "CIConvolution9Vertical" [36] = "CICopyMachineTransition" [37] = "CICrop" [38] = "CIDarkenBlendMode" [39] = "CIDifferenceBlendMode" [40] = "CIDisintegrateWithMaskTransition" [41] = "CIDissolveTransition" [42] = "CIDivideBlendMode" [43] = "CIDotScreen" [44] = "CIEightfoldReflectedTile" [45] = "CIExclusionBlendMode" [46] = "CIExposureAdjust" [47] = "CIFalseColor" [48] = "CIFlashTransition" [49] = "CIFourfoldReflectedTile" [50] = "CIFourfoldRotatedTile" [51] = "CIFourfoldTranslatedTile" [52] = "CIGammaAdjust" [53] = "CIGaussianBlur" [54] = "CIGaussianGradient" [55] = "CIGlassDistortion" [56] = "CIGlideReflectedTile" [57] = "CIGloom" [58] = "CIHardLightBlendMode" [59] = "CIHatchedScreen" [60] = "CIHighlightShadowAdjust" [61] = "CIHistogramDisplayFilter" [62] = "CIHoleDistortion" [63] = "CIHueAdjust" [64] = "CIHueBlendMode" [65] = "CILanczosScaleTransform" [66] = "CILightenBlendMode" [67] = "CILightTunnel" [68] = "CILinearBurnBlendMode" [69] = "CILinearDodgeBlendMode" [70] = "CILinearGradient" [71] = "CILinearToSRGBToneCurve" [72] = "CILineScreen" [73] = "CILuminosityBlendMode" [74] = "CIMaskToAlpha" [75] = "CIMaximumComponent" [76] = "CIMaximumCompositing" [77] = "CIMinimumComponent" [78] = "CIMinimumCompositing" [79] = "CIModTransition" [80] = "CIMultiplyBlendMode" [81] = "CIMultiplyCompositing" [82] = "CIOverlayBlendMode" [83] = "CIPerspectiveCorrection" [84] = "CIPhotoEffectChrome" [85] = "CIPhotoEffectFade" [86] = "CIPhotoEffectInstant" [87] = "CIPhotoEffectMono" [88] = "CIPhotoEffectNoir" [89] = "CIPhotoEffectProcess" [90] = "CIPhotoEffectTonal" [91] = "CIPhotoEffectTransfer" [92] = "CIPinchDistortion" [93] = "CIPinLightBlendMode" [94] = "CIPixellate" [95] = "CIQRCodeGenerator" [96] = "CIRadialGradient" [97] = "CIRandomGenerator" [98] = "CISaturationBlendMode" [99] = "CIScreenBlendMode" [100] = "CISepiaTone" [101] = "CISharpenLuminance" [102] = "CISixfoldReflectedTile" [103] = "CISixfoldRotatedTile" [104] = "CISmoothLinearGradient" [105] = "CISoftLightBlendMode" [106] = "CISourceAtopCompositing" [107] = "CISourceInCompositing" [108] = "CISourceOutCompositing" [109] = "CISourceOverCompositing" [110] = "CISRGBToneCurveToLinear" [111] = "CIStarShineGenerator" [112] = "CIStraightenFilter" [113] = "CIStripesGenerator" [114] = "CISubtractBlendMode" [115] = "CISwipeTransition" [116] = "CITemperatureAndTint" [117] = "CIToneCurve" [118] = "CITriangleKaleidoscope" [119] = "CITwelvefoldReflectedTile" [120] = "CITwirlDistortion" [121] = "CIUnsharpMask" [122] = "CIVibrance" [123] = "CIVignette" [124] = "CIVignetteEffect" [125] = "CIVortexDistortion" [126] = "CIWhitePointAdjust"} 目前来说提供了127个，我给你查出来了，你自己看着用吧，向Core Image的kCICategoryBuiltIn类别请求得到滤镜的名字
let filterNames = CIFilter.filterNamesInCategory(kCICategoryBuiltIn) as [String]
三、滤镜的基本使用
3.1 创建一个滤镜(使用滤镜名称，传给滤镜的初始化方法CIFilter就创建成功了)
let blurFilter=CIFilter(named:"CIGaussianBlur")
3.2 设置滤镜参数
滤镜的参数（比如上面创建了一个模糊滤镜）一般都是通过KVC的方式设置的，如下代码设置了模糊滤镜的模糊半径参数
blurFilter.setValue(12.0 forKey:"inputRadius")
3.3 创建使用滤镜的图像
Core Image要求使用滤镜的图像是CIImage类型，跟我们常用的UIImage不同，不过也很容易从UIImage创建，只需一行代码就能搞定
let inputImage=CIImage(image: sourceImageView.image)
3.4 将滤镜应用到图像上（其实是设置滤镜的一个很重要的属性：inputImage）
blurFilter.setValue(inputImage, forKey: "inputImage")
3.5 得到一个滤镜处理后的图片
处理后的图片是在当前的滤镜渲染上下文中，故而必须先得到当前的上下文，咱一切从简
let ciContext=CIContext(options: nil)
从当前的上下文中得到输出的图片，当然这也是一个CIImage类型的图啦，传入的参数就是滤镜的属性：outputImage
let cgImage = ciContext.createCGImage(blurFilter.outputImage, fromRect: inputImage.extent())
从这个CIImage也是一句代码得到我们熟悉的UIImage
resultImageView.image=UIImage(CGImage: cgImage)
得到的结果直接上图片
很明显的模糊效果出来啦……鼓掌吧别愣着了
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一个图片绝不仅仅只能施加一种滤镜效果，我们可以创建多个滤镜组成一条滤镜渲染的链条，只不过要注意每个滤镜的inputImage属性都是上一个滤镜的输出属性：inputImage，在上面给小猫咪模糊的基础上，我来改造下，让原图不仅高斯模糊，在添加一个单色滤镜，在添加一个晕影滤镜
//创建输入图像 let inputImage=CIImage(image: sourceImageView.image) //构建一个滤镜图表 let sepiaColor=CIColor(red: 0.6, green: 0.65, blue: 0.54) let monochromeFilter=CIFilter(name: "CIColorMonochrome", withInputParameters:["inputColor":sepiaColor,"inputIntensity":1.0]) monochromeFilter.setValue(inputImage, forKey: "inputImage") let blurFilter=CIFilter(name: "CIGaussianBlur") blurFilter.setValue(3.0, forKey: "inputRadius") blurFilter.setValue(monochromeFilter.outputImage, forKey: "inputImage") let vignetterFilter=CIFilter(name: "CIVignette", withInputParameters:["inputRadius":1.75,"inputIntensity":1.0]) vignetterFilter.setValue(blurFilter.outputImage, forKey: "inputImage") let outputImage=vignetterFilter.outputImage //得到一个滤镜处理后的图片 let ciContext=CIContext(options: nil) let cgImage=ciContext.createCGImage(outputImage, fromRect: inputImage.extent()) resultImageView.image=UIImage(CGImage: cgImage)
可以看到第一个单色滤镜monochromeFilter的inputImage就是原图像：monochromeFilter.setValue(inputImage, forKey: "inputImage")
第二个高斯模糊的滤镜blurFilter的inputImage是前一个滤镜的输出outputImage：blurFilter.setValue(monochromeFilter.outputImage, forKey: "inputImage")
第三个晕影的滤镜vignetterFilter的inputImage是前一个滤镜的输出outputImage：vignetterFilter.setValue(blurFilter.outputImage, forKey: "inputImage")
同时也看到滤镜的属性可以在创建的时候就设置上去
let vignetterFilter=CIFilter(name: "CIVignette", withInputParameters:["inputRadius":1.75,"inputIntensity":1.0])
最后附上三个滤镜的叠加效果，具体效果可根据参数的不同任意变幻
去制作你自己的美图秀秀吧……