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Asked: 2025-03-08 03:56:46 +0800 CST

为什么 iOS CILightenBlendMode 会改变灯光颜色？

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我有以下源图像：

在此处输入图片描述

我正在尝试将其转换为：

在此处输入图片描述

我已经建立了这个代码：

import CoreImage

if let image = UIImage(named: "demo9"), let editted = applyDuotoneEffect(to: image) {
    imageView.image = editted
}

func applyDuotoneEffect(to image: UIImage) -> UIImage? {
    guard let ciImage = CIImage(image: image) else { return nil }
    
    let context = CIContext(options: nil)
    
    let grayscaleFilter = CIFilter(name: "CIPhotoEffectMono", parameters: [kCIInputImageKey: ciImage])
    
    let solidLightColorImage = CIImage(color: CIColor(cgColor: ("efa403".toUIColor() ?? .red).cgColor)).cropped(to: ciImage.extent)
    let multiplyFilter = CIFilter(name: "CIMultiplyBlendMode", parameters: [kCIInputImageKey: grayscaleFilter?.outputImage as Any, kCIInputBackgroundImageKey: solidLightColorImage as Any])
       
    
    let solidDarkColorImage = CIImage(color: "290a59".toCIColor() ?? .black).cropped(to: ciImage.extent)
    let lightenFilter = CIFilter(name: "CILightenBlendMode", parameters: [kCIInputImageKey: multiplyFilter?.outputImage as Any, kCIInputBackgroundImageKey: solidDarkColorImage as Any])
    
    guard let outputImage = lightenFilter?.outputImage,
          let cgImage = context.createCGImage(outputImage, from: outputImage.extent) else { return nil }
    
    return UIImage(cgImage: cgImage)
}

extension String {
    func toUIColor() -> UIColor? {
        var cString = trimmingCharacters(in: .whitespacesAndNewlines).uppercased()
        
        if (cString.hasPrefix("#")) {
            cString.remove(at: cString.startIndex)
        }
        
        if ((cString.count) != 6) {
            return nil
        }
        
        var rgbValue: UInt64 = 0
        Scanner(string: cString).scanHexInt64(&rgbValue)
        
        return UIColor(
            red: CGFloat((rgbValue & 0xFF0000) >> 16) / 255.0,
            green: CGFloat((rgbValue & 0x00FF00) >> 8) / 255.0,
            blue: CGFloat(rgbValue & 0x0000FF) / 255.0,
            alpha: CGFloat(1.0)
        )
    }
}

但是，黄色背景在输出中看起来并不准确：

在此处输入图片描述

CILightenBlendMode我以为滤镜只会将黑色变成紫色，但实际上滤镜似乎也改变了黄色。我做错了什么？

1 个回答

  1. Best Answer

    双色调效果不起作用，因为CILightenBlendMode改变的不仅仅是黑色 - 它也影响了黄色。

    func applyDuotoneEffect(to image: UIImage) -> UIImage? {
    guard let ciImage = CIImage(image: image) else { return nil }
    
    let context = CIContext(options: nil)
    
    // Get grayscale
    let grayscaleFilter = CIFilter(name: "CIColorControls", parameters: [
        kCIInputImageKey: ciImage,
        kCIInputSaturationKey: 0.0
    ])
    
    // Use FalseColor filter - maps shadows to purple, highlights to yellow
    let falseColorFilter = CIFilter(name: "CIFalseColor", parameters: [
        kCIInputImageKey: grayscaleFilter?.outputImage as Any,
        "inputColor0": CIColor(hex: "290a59"), // Purple for shadows
        "inputColor1": CIColor(hex: "efa403")  // Yellow for highlights
    ])
    
    guard let outputImage = falseColorFilter?.outputImage,
          let cgImage = context.createCGImage(outputImage, from: outputImage.extent) else { return nil }
    
    return UIImage(cgImage: cgImage)
}

// Helper for hex colors
extension CIColor {
    convenience init(hex: String) {
        var cString = hex.trimmingCharacters(in: .whitespacesAndNewlines).uppercased()
        if cString.hasPrefix("#") { cString.remove(at: cString.startIndex) }
        var rgbValue: UInt64 = 0
        Scanner(string: cString).scanHexInt64(&rgbValue)
        self.init(
            red: CGFloat((rgbValue & 0xFF0000) >> 16) / 255.0,
            green: CGFloat((rgbValue & 0x00FF00) >> 8) / 255.0,
            blue: CGFloat(rgbValue & 0x0000FF) / 255.0
        )
    }
}

    修复：用滤镜替换混合模式CIFalseColor- 它专为双色调效果而设计。它只需一步即可将暗区映射为紫色，将亮区映射为黄色。

    • 1

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