Ios 使颜色变浅

昨天我遇到了一个情况，我需要使UIColor变亮，所以我创建了一个类别，并添加了一个

lighte

方法。我原以为直接将值乘以颜色的每个组成部分会很简单，但我的绿色开始变黄，所以我知道它必须更复杂

我提出的解决方案是将sRGB转换为线性，将颜色相乘，然后再转换回来。这似乎有效，但我不确定它是否“正确”。我在文档中找不到任何声明UIColor在sRGB空间中的内容。我也不是一个色彩科学家，所以我只有一个基本的数学知识

不管怎样，这是我的代码，我要求一些同行评审，看看是否有人对修改UIColor有更好的理解

CGFloat sRGB2Linear(CGFloat x){
    CGFloat a = 0.055;
    if(x <= 0.04045){
        return x * (1.0 / 12.92);
    }else{
        return pow((x + a) * (1.0 / (1 + a)), 2.4);
    }
}

CGFloat linear2sRGB(CGFloat x){
    CGFloat a = 0.055;
    if(x <= 0.0031308){
        return x * 12.92;
    }else{
        return (1 + a) * pow(x, 1 / 2.4) - a;
    }
}

- (UIColor *)lighten:(CGFloat)value{
    const CGFloat *components = CGColorGetComponents([self CGColor]);
    CGFloat newR = (sRGB2Linear(components[0])+1)*value;
    CGFloat newG = (sRGB2Linear(components[1])+1)*value;
    CGFloat newB = (sRGB2Linear(components[2])+1)*value;
    newR = MAX(0, MIN(1, linear2sRGB(newR)));
    newG = MAX(0, MIN(1, linear2sRGB(newG)));
    newB = MAX(0, MIN(1, linear2sRGB(newB)));
    return [UIColor colorWithRed:newR green:newG blue:newB alpha:components[3]];
}

CGFloat sRGB2Linear（CGFloat x）{
CGA=0.055；
如果（x，则可以使用色调、饱和度和亮度

使用

- (BOOL)getHue:(CGFloat *)hue saturation:(CGFloat *)saturation brightness:(CGFloat *)brightness alpha:(CGFloat *)alpha

然后调整亮度，并构建新颜色：

- (UIColor *)initWithHue:(CGFloat)hue saturation:(CGFloat)saturation brightness:(CGFloat)brightness alpha:(CGFloat)alpha

请记住，您需要向第一个函数传递指针。
这是我的iOS5+解决方案，可以轻松更改相对亮度（一体式变亮和变暗）：

它是这样调用的：

[self changeBrightness:someUiColor amount:1.1]

使用1.1将使亮度增加10%；0.9将使亮度减少10%。请注意，10%是相对于纯白色的（即，10%始终是亮度增加0.1%）如果您希望增加百分比，使颜色始终变亮或变暗，而不管其初始亮度如何，这是预期的行为。
我改进了ank的方法，允许修改饱和度和色调

输入按百分比处理，因此1.0的
b
等于100%（无变化）。要将亮度减弱30%，请将
b
设置为0.7

+ (UIColor*)changeColor:(UIColor*)color brightness:(CGFloat)b saturation:(CGFloat)s hue:(CGFloat)h
{

    CGFloat hue, saturation, brightness, alpha;
    if ([color getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha]) {
        brightness *= b;
        brightness = MAX(MIN(brightness, 1.0), 0.0);
        saturation *= s;
        saturation = MAX(MIN(saturation, 1.0), 0.0);
        hue *= h;
        hue = MAX(MIN(hue, 1.0), 0.0);
        return [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:alpha];
    }

    CGFloat white;
    if ([color getWhite:&white alpha:&alpha]) {
        white += (b-1.0);
        white = MAX(MIN(b, 1.0), 0.0);
        return [UIColor colorWithWhite:white alpha:alpha];
    }

    return nil;
}

试一试

它应该返回与您的颜色混合的白色

因此，您可以将alpha设置为0.2，我认为这是可以的

extension UIColor {
    public func changeBrightness(b: CGFloat, saturation s: CGFloat = 1.0, hue h: CGFloat = 1.0) -> UIColor? {
        var hue : CGFloat = 0.0
        var saturation : CGFloat = 0.0
        var brightness : CGFloat = 0.0
        var alpha : CGFloat = 0.0

        if self.getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha) {
            brightness *= b
            brightness = max(min(brightness, 1.0), 0.0)
            saturation *= s
            saturation = max(min(saturation, 1.0), 0.0)
            hue *= h
            hue = max(min(hue, 1.0), 0.0)

            return UIColor(hue: hue, saturation: saturation, brightness: brightness, alpha: alpha)
        }

        var white: CGFloat = 0.0
        if self.getWhite(&white, alpha: &alpha) {
            white += (b - 1.0)
            white = max(min(b, 1.0), 0.0)

            return UIColor(white: white, alpha: alpha)
        }

        return nil
    }
}

==1.0是提供的颜色，>1.0是较浅的颜色，与白色混合是我发现的唯一不会扭曲原始颜色的方法，就像在这个快速扩展中：

extension UIColor {

    @objc func lighten(_ alpha: CGFloat) -> UIColor {
        var r: CGFloat = 0
        var g: CGFloat = 0
        var b: CGFloat = 0
        var a: CGFloat = 0
        guard self.getRed(&r, green: &g, blue: &b, alpha: &a) else { return self }
        return UIColor(red:r + (1.0-r) * alpha, green:g + (1.0-g) * alpha, blue:b + (1.0-b) * alpha, alpha: a)
    }
}

extension UIColor {
    public func changeBrightness(b: CGFloat, saturation s: CGFloat = 1.0, hue h: CGFloat = 1.0) -> UIColor? {
        var hue : CGFloat = 0.0
        var saturation : CGFloat = 0.0
        var brightness : CGFloat = 0.0
        var alpha : CGFloat = 0.0

        if self.getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha) {
            brightness *= b
            brightness = max(min(brightness, 1.0), 0.0)
            saturation *= s
            saturation = max(min(saturation, 1.0), 0.0)
            hue *= h
            hue = max(min(hue, 1.0), 0.0)

            return UIColor(hue: hue, saturation: saturation, brightness: brightness, alpha: alpha)
        }

        var white: CGFloat = 0.0
        if self.getWhite(&white, alpha: &alpha) {
            white += (b - 1.0)
            white = max(min(b, 1.0), 0.0)

            return UIColor(white: white, alpha: alpha)
        }

        return nil
    }
}

- (UIColor *)changeBrightnessToPercentage:(CGFloat)percentage {
    CGFloat hue, saturation, brightness, alpha;
    if ([self getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha]) {
        brightness += (percentage - 1.0);
        brightness = MAX(MIN(brightness, 1.0), 0.0);
        return [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:alpha];
    }

    CGFloat white;
    if ([self getWhite:&white alpha:&alpha]) {
        white += (percentage - 1.0);
        white = MAX(MIN(white, 1.0), 0.0);
        return [UIColor colorWithWhite:white alpha:alpha];
    }

    return nil;
}

extension UIColor {

    @objc func lighten(_ alpha: CGFloat) -> UIColor {
        var r: CGFloat = 0
        var g: CGFloat = 0
        var b: CGFloat = 0
        var a: CGFloat = 0
        guard self.getRed(&r, green: &g, blue: &b, alpha: &a) else { return self }
        return UIColor(red:r + (1.0-r) * alpha, green:g + (1.0-g) * alpha, blue:b + (1.0-b) * alpha, alpha: a)
    }
}