在 Swift 中使用 CIColorMatrix 过滤器

Question

以下 Swift 函数应该使用指定的 'tintColor' 为灰度图像 'greyImage' 着色：

import UIKit

func colorizeImage(greyImage : UIImage, tintColor : UIColor) -> UIImage? {

    let colorMatrixFilter = CIFilter(name: "CIColorMatrix")

    var r:CGFloat = 0
    var g:CGFloat = 0
    var b:CGFloat = 0
    var a:CGFloat = 0
    tintColor.getRed(&r, green:&g, blue:&b, alpha:&a)

    colorMatrixFilter.setDefaults()
    colorMatrixFilter.setValue(greyImage, forKey:"inputImage") //kCIInputImageKey)
    colorMatrixFilter.setValue(CIVector(x:r, y:0, z:0, w:0), forKey:"inputRVector")
    colorMatrixFilter.setValue(CIVector(x:0, y:g, z:0, w:0), forKey:"inputGVector")
    colorMatrixFilter.setValue(CIVector(x:0, y:0, z:b, w:0), forKey:"inputBVector")
    colorMatrixFilter.setValue(CIVector(x:0, y:0, z:0, w:a), forKey:"inputAVector")

    if let ciImage =  colorMatrixFilter.outputImage {
        return UIImage(CIImage: ciImage);
    }

    return nil;
}

颜色为UIColor.orangeColor() (r=1,g=0.5,b=0,a=1)，灰度图可以，输入ImageView时显示正常。

看起来提供了所有必要的键并且键分配顺利（顺便说一句，过滤器检查键的有效性，还是获取所有内容？），但是读取 'outputImage' 属性会产生 SIGABRT 和以下控制台消息：

2015-05-02 13:04:07.319 MyApp[436:8241] -[UIImage _internalRepresentation]: unrecognized selector sent to instance 0x7fd5b3ca82b0
2015-05-02 13:04:07.629 MyApp[436:8241] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIImage _internalRepresentation]: unrecognized selector sent to instance 0x7fd5b3ca82b0'
*** First throw call stack:
(
    0   CoreFoundation                      0x00000001087abf35 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x000000010a56cbb7 objc_exception_throw + 45
    2   CoreFoundation                      0x00000001087b304d -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
    3   CoreFoundation                      0x000000010870b27c ___forwarding___ + 988
    4   CoreFoundation                      0x000000010870ae18 _CF_forwarding_prep_0 + 120
    5   CoreImage                           0x0000000108bd30fe -[CIColorMatrix outputImage] + 885
    6   MyApp                            0x00000001085c182d _TF8MyApp13colorizeImageFTCSo7UIImageCSo7UIColor_GSqS0__ + 4733
    7   MyApp                            0x00000001085c2b59 

Answer 1

问题在于CIColorMatrix 期望参数 inputImage 应该是 CIImage 对象而不是 UIImage (greyImage)。

更新：Swift 3 或更高版本

extension UIColor {
    var rgba: (red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat)? {
        var (r,g,b,a): (CGFloat,CGFloat,CGFloat,CGFloat) = (0,0,0,0)
        return getRed(&r, green: &g, blue: &b, alpha: &a) ? (r,g,b,a) : nil
    }
}

---

extension CIImage {
    var image: UIImage { .init(ciImage: self) }
    func colorized(with color: UIColor) -> CIImage? {
        guard
            let (r,g,b,a) = color.rgba,
            let colorMatrix = CIFilter(name: "CIColorMatrix",
                parameters: ["inputImage":  self,
                             "inputRVector": CIVector(x: r, y: 0, z: 0, w: 0),
                             "inputGVector": CIVector(x: 0, y: g, z: 0, w: 0),
                             "inputBVector": CIVector(x: 0, y: 0, z: b, w: 0),
                             "inputAVector": CIVector(x: 0, y: 0, z: 0, w: a)])
        else { return nil }
        return colorMatrix.outputImage
    }
}

---

extension UIImage {
    var coreImage: CIImage? { CIImage(image: self) }
    func colorized(with color: UIColor) -> UIImage? {
        coreImage?.colorized(with: color)?.image
    }
}

---

游乐场测试：

let profilePicture = UIImage(data: try! Data(contentsOf: URL(string: "http://i.stack.imgur.com/Xs4RX.jpg")!))!
profilePicture.colorized(with: .orange)

---