从源自十六进制颜色的 UIColors 获取 RGB 值 [英] Getting RGB values from UIColors derived from Hex colors

问题描述

尝试从 UIColor 检索 RGB 值.但是， -[UIColor getRed:blue:green:alpha] 在我的情况下不起作用.该方法从不返回 YES，我认为这意味着颜色无法转换为 RGB.我认为这是因为我的 UIColor 是从十六进制颜色生成的(例如:#CCCCCC).

Trying to retrieve RGB values from a UIColor. However, -[UIColor getRed:blue:green:alpha] is not working in my case. The method never returns YES which I think means that the color is not convertible into RGB. I assume this is because my UIColor was generated from a Hex color (ex: #CCCCCC).

你到底是如何从 iOS 中基于十六进制的 UIColors 获得 RGB 值的?

How the heck do you get RGB values from hex-based UIColors in iOS?

推荐答案

问题在于您给出的示例.颜色 #CCCCCC 是一种灰度颜色，这意味着 UIColor 不是用 RGB 创建的，而是用灰色创建的.换句话说，它是用 UIColor colorWithWhite:alpha: 创建的.由于您的 UIColor 是使用与 RGB 不同的颜色模型创建的，因此使用 getRed:green:blue:alpha: 返回 NO.

The problem is with the example you give. The color #CCCCCC is a greyscale color meaning the UIColor is not created with RGB but with a grey. In other words, it is created with UIColor colorWithWhite:alpha:. Since your UIColor is created with a different color model than RGB, using getRed:green:blue:alpha: returns NO.

你能做的是:-

UIColor *color =  // your color
CGFloat red, green, blue, alpha;

if (![color getRed:&red green:&green blue:&blue alpha:&alpha]) {

    CGFloat white;
    if ([color getWhite:&white alpha:&alpha]) {
        red = green = blue = white;
    } else {
        NSLog(@"Uh oh, not RGB or greyscale");
    }
}

更新:

似乎从 iOS 8 开始，行为发生了一些变化.使用 UIColor colorWithWhite:alpha: 创建的颜色的 RGB 值可以通过 UIColor getRed:green:blue 获得:阿尔法:.在早期版本的 iOS 中，这不起作用.因此需要我最初发布的代码.

It seems that the behavior changed a bit as of iOS 8. The RGB values of a color created with UIColor colorWithWhite:alpha: can be obtained with UIColor getRed:green:blue:alpha:. In earlier versions of iOS, this didn't work. Hence the need for the code I originally posted.

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