ios Swift CAGradientLayer显示不准确的颜色

u1ehiz5o 于 2023-03-05 发布在 iOS

关注(0)|答案(1)|浏览(143)

我正在使用CAGradientLayer添加一个渐变到我的UIView。我正在设置渐变为纯红色测试，当我检查显示的颜色时，它显示的RGB值与我指定的不同。有没有方法可以确保渐变显示我设置的颜色？

let gradientLayer2 = CAGradientLayer()
gradientLayer2.frame.size = colourPickerView.frame.size
gradientLayer2.colors = [
    UIColor(red: 1.00, green: 0.00, blue: 0.00, alpha: 1.00).cgColor
    UIColor(red: 1.00, green: 0.00, blue: 0.00, alpha: 1.00).cgColor,
]
    
gradientLayer2.startPoint = CGPoint(x: 0.0, y: 0.0)
gradientLayer2.endPoint = CGPoint(x: 1, y: 0)
gradientLayer2.cornerRadius = 20
colourPickerView.layer.insertSublayer(gradientLayer2, at: 0)

这将红色显示为：<CGColor 0x283c8e400> [<CGColorSpace 0x283c989c0> (kCGColorSpaceICCBased; kCGColorSpaceModelRGB; sRGB IEC61966-2.1; extended range)] ( 1 0.14902 0 1 )（请注意，绿色值显示为“0.14902”）
当我添加一个纯色的背景色到图层，而不是一个梯度，它确实显示正确的RGB值。

let layer = CALayer()
layer.frame.size = colourPickerView.frame.size
layer.backgroundColor = UIColor(red: 1.00, green: 0.00, blue: 0.00, alpha: 1.00).cgColor
colourPickerView.layer.insertSublayer(layer, at: 0)

下面是我用来获取某个像素的颜色的代码：

extension UIView {
func colorOfPointView(point: CGPoint) -> UIColor {
    let colorSpace: CGColorSpace = CGColorSpaceCreateDeviceRGB()
    let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)

    var pixelData: [UInt8] = [0, 0, 0, 0]

    let context = CGContext(data: &pixelData, width: 1, height: 1, bitsPerComponent: 8, bytesPerRow: 4, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)

    context!.translateBy(x: -point.x, y: -point.y)

    self.layer.render(in: context!)

    let red: CGFloat = CGFloat(pixelData[0]) / CGFloat(255.0)
    let green: CGFloat = CGFloat(pixelData[1]) / CGFloat(255.0)
    let blue: CGFloat = CGFloat(pixelData[2]) / CGFloat(255.0)
    let alpha: CGFloat = CGFloat(pixelData[3]) / CGFloat(255.0)

    let color: UIColor = UIColor(red: red, green: green, blue: blue, alpha: alpha)

    return color
}

ios

来源：https://stackoverflow.com/questions/75629031/swift-cagradientlayer-showing-inaccurate-color

1条答案

按热度按时间

efzxgjgh1#

奇怪！这是唯一涉及这部分代码的代码吗？我刚刚测试过，得到了真实的结果：

Optional([<CGColor 0x6000002bd6e0> [<CGColorSpace 0x6000002b9980> (kCGColorSpaceICCBased; kCGColorSpaceModelRGB; sRGB IEC61966-2.1; extended range)] ( 1 0 0 1 ), <CGColor 0x6000002bd2c0> [<CGColorSpace 0x6000002b9980> (kCGColorSpaceICCBased; kCGColorSpaceModelRGB; sRGB IEC61966-2.1; extended range)] ( 1 0 0 1 )])

将这段代码复制并粘贴到一个新的Xcode项目中，然后检查是否仍然得到错误的结果。

import UIKit

class ViewController: UIViewController {

    let gradientLayer2 = CAGradientLayer()
    let slider = UISlider(frame: CGRect(x: 10, y: 400, width: 100, height: 50))

    override func viewDidLoad() {
        super.viewDidLoad()
        
        slider.maximumValue = 1
        slider.minimumValue = 0
        slider.addTarget(self, action: #selector(sliderChanged), for: .valueChanged)
        slider.backgroundColor = .red
        gradientLayer2.frame.size = CGSize(width: 200, height: 200)
        gradientLayer2.colors = [
            UIColor(red: 1.00, green: 0.00, blue: 0.00, alpha: 1.00).cgColor,
            UIColor(red: 1.00, green: 0.00, blue: 0.00, alpha: 1.00).cgColor
        ]
            
        gradientLayer2.startPoint = CGPoint(x: 0.0, y: 0.0)
        gradientLayer2.endPoint = CGPoint(x: 1, y: 0)
        gradientLayer2.cornerRadius = 20
        view.layer.insertSublayer(gradientLayer2, at: 0)
        view.addSubview(slider)
       
    }

    @objc func sliderChanged()
    {
        gradientLayer2.colors = [
            UIColor(red: 1.00, green: 0.00, blue: 0.00, alpha: 1.00).cgColor,
            UIColor(red: CGFloat(slider.value), green: 0.00, blue: 0.00, alpha: 1.00).cgColor
        ]
        print(gradientLayer2.colors)
    }

}

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ios Swift CAGradientLayer显示不准确的颜色

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