为什么SwiftUI中Image和CIImage之间的亮度过滤器不同？

如何解决为什么SwiftUI中Image和CIImage之间的亮度过滤器不同？

我正在调整图像的亮度。

首先，我使用 SwiftUI图像来显示图像：

Image(xxx)
    .brightness(-0.5)

然后，我使用 CIImage 通过这种亮度调整来生成新图像：

func drawPic(img: UIImage) -> UIImage {
    let cgimage: CGImage = img.cgImage!
    let image = CIImage(cgImage: cgimage)
    let parameters = [
        "inputBrightness": Float(-0.5)
    ]
    let outputImage = image.applyingFilter("CIColorControls",parameters: parameters)
    let contextv = CIContext(options: nil)
    let CgPic = contextv.createCGImage(outputImage,from: outputImage.extent)!
    return UIImage(cgImage: CgPic)
}

但是当我预览这些图像时，我发现它们的颜色并不相同：

谁能告诉我为什么以及如何解决这个问题？

所有代码：

import SwiftUI
import UIKit
import CoreImage
import CoreImage.CIFilterBuiltins

struct TestImage: View {
    var body: some View {
        VStack{
            Image("colorcircle2").resizable().frame(width: 200,height: 200,alignment: /*@START_MENU_TOKEN@*/.center/*@END_MENU_TOKEN@*/)
            Text("Original Image").padding(.bottom,24.0)
            Image("colorcircle2").resizable().frame(width: 200,alignment: /*@START_MENU_TOKEN@*/.center/*@END_MENU_TOKEN@*/).brightness(-0.5)
            Text("SwiftUI Image").padding(.bottom,24.0)
            Image(uiImage: drawPic(img: UIImage(imageLiteralResourceName: "colorcircle2"))).resizable().frame(width: 200,alignment: /*@START_MENU_TOKEN@*/.center/*@END_MENU_TOKEN@*/)
            Text("CIImage").padding(.bottom,24.0)
        }
    }
}

func drawPic(img: UIImage) -> UIImage {
    let cgimage: CGImage = img.cgImage!
    let image = CIImage(cgImage: cgimage)
    let parameters = [
        "inputBrightness": Float(-0.5)
    ]
    let outputImage = image.applyingFilter("CIColorControls",from: outputImage.extent)!
    return UIImage(cgImage: CgPic)
}


struct TestImage_Previews: PreviewProvider {
    static var previews: some View {
        TestImage()
    }
}