如何从 UIColor 对象获取红绿蓝 (RGB) 和 alpha？

Question

我得到从此方法返回的 UIColor：

- (UIColor *)getUserSelectedColor {   
    return [UIColor colorWithRed:redSlider.value green:greenSlider.value blue:blueSlider.value alpha:1.0];
}

并得到这样的颜色：

UIColor *selectedColor = [(ColorPickerView *)alertView getUserSelectedColor];

现在我想从 selectedColor 中获取红色、绿色、蓝色，以便使用这些值。我想要 0 到 1 之间的值。

Answer 1

的原因崩溃时访问SelectedColor.CGColor可能是因为你不保留从getColor的结果，也许你需要的是：

SelectedColor = [[(ColorPickerView *)alertView getColor] retain];

您只能从正在使用的RGB色彩空间，因为你正在使用UIColor这不是一个问题colorWithRed:green:blue:alpha: RGB颜色成分，但如果你的代码的变化而变化这一点。

通过这介意颜色分量是很容易的：

const CGFloat* components = CGColorGetComponents(SelectedColor.CGColor);
NSLog(@"Red: %f", components[0]);
NSLog(@"Green: %f", components[1]); 
NSLog(@"Blue: %f", components[2]);
NSLog(@"Alpha: %f", CGColorGetAlpha(SelectedColor.CGColor));

Answer 2

此解决方案适用于非RGB颜色以及例如黑色或白色。

UIColor *color = [UIColor blackColor];
CGFloat red = 0.0, green = 0.0, blue = 0.0, alpha = 0.0;
// iOS 5
if ([color respondsToSelector:@selector(getRed:green:blue:alpha:)]) {
     [color getRed:&red green:&green blue:&blue alpha:&alpha];
} else {
     // < iOS 5
     const CGFloat *components = CGColorGetComponents(color.CGColor);
     red = components[0];
     green = components[1];
     blue = components[2];
     alpha = components[3];
}

// This is a non-RGB color
if(CGColorGetNumberOfComponents(color.CGColor) == 2) {
    CGFloat hue;
    CGFloat saturation;
    CGFloat brightness;
    [color getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha];

}

Answer 3

在大多数情况下，这将工作，除非转换到RGB不起作用。

float red, green, blue, alpha;
BOOL conversionToRGBWentOk = [color getRed:&red green:&green blue:&blue alpha:&alpha];

这就是这些方法是，在事实。如果conversionToRGBWentOk被NO你就会有一个问题，虽然。

Answer 4

我想你应该有一个一看这里，其中人工鱼礁引导显示了如何支持扩展UIColor类用于访问颜色分量。

Answer 5

你只是简单的做这个

CGFloat red,green,blue,alpha;

[UIColorobject getRed:&red green:&green blue:&blue alpha:&alpha];

在红，绿，蓝和阿尔法你RGB值 如果您有任何疑问，请咨询......

由于

Answer 6

该代码段应与RGB和灰度工作：

CGFloat *components = (CGFloat *) CGColorGetComponents(<UIColor instance>.CGColor);
if(CGColorGetNumberOfComponents(<UIColor instance>.CGColor) == 2)
{
  //assuming it is grayscale - copy the first value
  components[2] = components[1] = components[0];
}

Answer 7

我认为这将是很长的路要走。如果需要使用的α-参数，以及，可以从输入像您的R G和B做内插的α。

- (UIColor *)getColorBetweenColor:(UIColor *)color1 andColor:(UIColor *)color2 percentage:(CGFloat)percent {
    CGFloat red1, green1, blue1, alpha1;
    CGFloat red2, green2, blue2, alpha2;

    [color1 getRed:&red1 green:&green1 blue:&blue1 alpha:&alpha1];
    [color2 getRed:&red2 green:&green2 blue:&blue2 alpha:&alpha2];

    double resultRed = red1 + percent * (red2 - red1);
    double resultGreen = green1 + percent * (green2 - green1);
    double resultBlue = blue1 + percent * (blue2 - blue1);

    return [UIColor colorWithRed:resultRed green:resultGreen blue:resultBlue alpha:1];
}

Answer 8

有一个夫特扩展为：）

extension UIColor {

    var rgba: (red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat) {
        var red: CGFloat = 0.0
        var green: CGFloat = 0.0
        var blue: CGFloat = 0.0
        var alpha: CGFloat = 0.0
        getRed(&red, green: &green, blue: &blue, alpha: &alpha)

        return (red: red, green: green, blue: blue, alpha: alpha)
    }

    var redComponent: CGFloat {
        var red: CGFloat = 0.0
        getRed(&red, green: nil, blue: nil, alpha: nil)

        return red
    }

    var greenComponent: CGFloat {
        var green: CGFloat = 0.0
        getRed(&green, green: nil, blue: nil, alpha: nil)

        return green
    }

    var blueComponent: CGFloat {
        var blue: CGFloat = 0.0
        getRed(nil, green: nil, blue: &blue, alpha: nil)

        return blue
    }

    var alphaComponent: CGFloat {
        var alpha: CGFloat = 0.0
        getRed(nil, green: nil, blue: nil, alpha: &alpha)

        return alpha
    }
}

它与夫特4.2兼容并且还与2个部件的颜色，如黑色，灰色等。 可以访问特定的运河像这样：

myColor.rgba.blue

或者，其等效的：

myColor.blueComponent

Answer 9

只需添加属性即可 ColorLiteral 如示例所示。Xcode 将提示您提供可供选择的完整颜色列表。

self.view.backgroundColor = ColorLiteral 

Answer 10

下面是我已经为这个和其它的色彩控制取得了一些有用的宏：

在你的情况，你只想用

getRGBA(myColor, red, green, blue, alpha);

NSLog(@"Red Value: %f", red);
NSLog(@"Blue Value: %f", green);
NSLog(@"Green Value: %f", blue);

---

宏：

#define rgba(r,g,b,a) [UIColor colorWithRed:((float)(r))/255.0f green:((float)(g))/255.0f blue:((float)(b))/255.0f alpha:a]
#define rgb(r,g,b) rgba(r, g, b, 1.0f)

#define rgbaf(r,g,b,a) [UIColor colorWithRed:(r) green:(g) blue:(b) alpha:a]
#define rgbf(r,g,b) rgbaf(r, g, b, 1.0f)

#define rgba_fromColor(__color, __r, __g, __b, __a) \
CGFloat __r, __g, __b, __a;\
UIColor *__unpackedColor = [NSKeyedUnarchiver unarchiveObjectWithData:[NSKeyedArchiver archivedDataWithRootObject:__color]];/*Bring system colors into compatible color-space (e.g. DarkGrayColor)*/\
[__unpackedColor getRed:&__r green:&__g blue:&__b alpha:&__a];
#define getRGBA(__color, __r, __g, __b, __a) rgba_fromColor(__color, __r, __g, __b, __a)

#define getRed(__color)  (\
(^float (void){\
rgba_fromColor(__color, r, g, b, a);\
return r;\
})()\
)

#define getGreen(__color)  (\
(^float (void){\
rgba_fromColor(__color, r, g, b, a);\
return g;\
})()\
)

#define getBlue(__color)  (\
(^float (void){\
rgba_fromColor(__color, r, g, b, a);\
return b;\
})()\
)

#define getAlpha(__color)  (\
(^float (void){\
rgba_fromColor(__color, r, g, b, a);\
return a;\
})()\
)










#define hsba(h,s,b,a) [UIColor colorWithHue:((float)(h))/360.0f saturation:((float)(s))/100.0f brightness:((float)(b))/100.0f alpha:a]
#define hsb(h,s,b) hsba(h, s, b, 1.0f)

#define hsbaf(h,s,b,a) [UIColor colorWithHue:(h) saturation:(s) brightness:(b) alpha:a]
#define hsbf(h,s,b) rgbaf(h, s, b, 1.0f)

#define hsba_fromColor(__color, __h, __s, __b, __a) \
CGFloat __h, __s, __b, __a;\
UIColor *__unpackedColor = [NSKeyedUnarchiver unarchiveObjectWithData:[NSKeyedArchiver archivedDataWithRootObject:__color]];/*Bring system colors into compatible color-space (e.g. DarkGrayColor)*/\
[__unpackedColor getHue:&__h saturation:&__s brightness:&__b alpha:&__a];
#define getHSBA(__color, __h, __s, __b, __a) hsba_fromColor(__color, __h, __s, __b, __a)

#define getHue(__color)  (\
(^float (void){\
hsba_fromColor(__color, h, s, b, a);\
return h;\
})()\
)

#define getSaturation(__color)  (\
(^float (void){\
hsba_fromColor(__color, h, s, b, a);\
return s;\
})()\
)

#define getBrightness(__color)  (\
(^float (void){\
hsba_fromColor(__color, h, s, b, a);\
return b;\
})()\
)

/*
///already defined in RGBA macros
#define getAlpha(__color)  (\
(^float (void){\
hsba_fromColor(__color, h, s, b, a);\
return a;\
})()\
)
*/