blocks|key|3267852|text|对于不是浅灰色的所有东西，颜色的RGB反转通常与之形成强烈的对比。演示只是反转颜色和去饱和度(将其转换为灰色)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3267853|但是生成一个很好的平滑的颜色组合是相当复杂的。请看：|3267854|http://particletree.com/notebook/calculating-color-contrast-for-legible-text/|offset|length|3267855|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|25|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Q|8|@]|9|@$F|R|G|S|1|T]]|A|$]]|$1|H|3|-4|5|6|7|U|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|E]]]]

For everything that's not grayish, the RGB inverse of a color is usually highly contrasted with it. 
The demo just inverts the color and desaturates it (converts it to a gray).

But generating a nice soothing combination of colors is quite complicated. 
Look at :

<a href="http://particletree.com/notebook/calculating-color-contrast-for-legible-text/" rel="nofollow noreferrer">http://particletree.com/notebook/calculating-color-contrast-for-legible-text/</a>

blocks|key|3267886|text|如果你想知道颜色的亮度，这里有一些伪代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3267887|public+float+GetBrightness(int+red,+int+blue,+int+green)
{
++++float+num+=+red+/+255f;
++++float+num2+=+blue+/+255f;
++++float+num3+=+green+/+255f;
++++float+num4+=+num;
++++float+num5+=+num;
++++if+(num2+>+num4)
++++++++num4+=+num2;
++++if+(num3+>+num4)
++++++++num4+=+num3;
++++if+(num2+<+num5)
++++++++num5+=+num2;
++++if+(num3+<+num5)
++++++++num5+=+num3;
++++return+((num4+%2B+num5)+/+2f);
}|code-block|syntax|javascript|3267888|如果该值>+0.5，则为亮，否则为暗。|3267889|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

If you want to find the brightness of the color, here is some pseudo code:

<pre><code>public float GetBrightness(int red, int blue, int green)
{
 float num = red / 255f;
 float num2 = blue / 255f;
 float num3 = green / 255f;
 float num4 = num;
 float num5 = num;
 if (num2 &gt; num4)
 num4 = num2;
 if (num3 &gt; num4)
 num4 = num3;
 if (num2 &lt; num5)
 num5 = num2;
 if (num3 &lt; num5)
 num5 = num3;
 return ((num4 + num5) / 2f);
}
</code></pre>

If it is > 0.5 it is bright, and otherwise dark.

blocks|key|3267912|text|W3C具有以下特性：http://www.w3.org/WAI/ER/WD-AERT/#color-contrast|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3267913|如果只处理黑色或白色文本，请使用上面的颜色亮度计算。如果低于125，请使用白色文本。如果是125或以上，请使用黑色文本。|3267914|编辑1:偏向黑色文本。:)|3267915|编辑2:使用公式为((红值*+299)+%2B(绿值*+587)+%2B(蓝值*+114))+/+1000。|3267916|entityMap|0|LINK|mutability|MUTABLE|url|http://www.w3.org/WAI/ER/WD-AERT/#color-contrast^0|A|1C|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@$A|S|B|T|1|U]]|C|$]]|$1|D|3|E|5|6|7|V|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|W|8|@]|9|@]|C|$]]|$1|H|3|I|5|6|7|X|8|@]|9|@]|C|$]]|$1|J|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|K|$L|$5|M|N|O|C|$P|Q]]]]

W3C has the following:
<a href="http://www.w3.org/WAI/ER/WD-AERT/#color-contrast" rel="noreferrer">http://www.w3.org/WAI/ER/WD-AERT/#color-contrast</a>

If you're only doing black or white text, use the color brightness calculation above. If it is below 125, use white text. If it is 125 or above, use black text.

edit 1: bias towards black text. :)

edit 2: The formula to use is ((Red value * 299) + (Green value * 587) + (Blue value * 114)) / 1000.

blocks|key|3267933|text|使用Erik+Nedwidek的答案，我想出了一小段代码，以便于包含。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3267934|-+(UIColor+*)readableForegroundColorForBackgroundColor:(UIColor*)backgroundColor+{
++++size_t+count+=+CGColorGetNumberOfComponents(backgroundColor.CGColor);
++++const+CGFloat+*componentColors+=+CGColorGetComponents(backgroundColor.CGColor);

++++CGFloat+darknessScore+=+0;
++++if+(count+==+2)+{
++++++++darknessScore+=+(((componentColors[0]*255)+*+299)+%2B+((componentColors[0]*255)+*+587)+%2B+((componentColors[0]*255)+*+114))+/+1000;
++++}+else+if+(count+==+4)+{
++++++++darknessScore+=+(((componentColors[0]*255)+*+299)+%2B+((componentColors[1]*255)+*+587)+%2B+((componentColors[2]*255)+*+114))+/+1000;
++++}

++++if+(darknessScore+>=+125)+{
++++++++return+[UIColor+blackColor];
++++}

++++return+[UIColor+whiteColor];
}|code-block|syntax|javascript|3267935|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Using Erik Nedwidek's answer, I came up with that little snippet of code for easy inclusion.

<pre><code>- (UIColor *)readableForegroundColorForBackgroundColor:(UIColor*)backgroundColor {
 size_t count = CGColorGetNumberOfComponents(backgroundColor.CGColor);
 const CGFloat *componentColors = CGColorGetComponents(backgroundColor.CGColor);

 CGFloat darknessScore = 0;
 if (count == 2) {
 darknessScore = (((componentColors[0]*255) * 299) + ((componentColors[0]*255) * 587) + ((componentColors[0]*255) * 114)) / 1000;
 } else if (count == 4) {
 darknessScore = (((componentColors[0]*255) * 299) + ((componentColors[1]*255) * 587) + ((componentColors[2]*255) * 114)) / 1000;
 }

 if (darknessScore &gt;= 125) {
 return [UIColor blackColor];
 }

 return [UIColor whiteColor];
}
</code></pre>

blocks|key|310607|text|-+(BOOL)isColorLight:(UIColor*)color
{
++++CGFloat+white+=+0;
++++[color+getWhite:&white+alpha:nil];
++++return+(white+>=+.85);
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|310608|新增Swift+5版本：|unstyled|offset|length|style|CODE|310609|var+white:+CGFloat+=+0.0
color.getWhite(&white,+alpha:+nil)
return+white+>=+.85+//+Don't+use+white+background|310610|entityMap^0|0|2|7|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|P|8|@$G|Q|H|R|I|J]]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$B|C]]|$1|M|3|-4|5|F|7|T|8|@]|9|@]|A|$]]]|N|$]]

<pre><code>- (BOOL)isColorLight:(UIColor*)color
{
 CGFloat white = 0;
 [color getWhite:&amp;white alpha:nil];
 return (white &gt;= .85);
}
</code></pre>

Added <code>Swift 5</code> version:

<pre><code>var white: CGFloat = 0.0
color.getWhite(&amp;white, alpha: nil)
return white &gt;= .85 // Don't use white background
</code></pre>

blocks|key|3054350|text|如果您更喜欢数据块版本：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3054351|BOOL+(%5EisDark)(UIColor+*)+=+%5E(UIColor+*color){
++++const+CGFloat+*component+=+CGColorGetComponents(color.CGColor);
++++CGFloat+brightness+=+((component[0]+*+299)+%2B+(component[1]+*+587)+%2B+(component[2]+*+114))+/+1000;

++++if+(brightness+<+0.75)
++++++++return++YES;
++++return+NO;
};|code-block|syntax|javascript|3054352|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you prefer the block version:

<pre><code>BOOL (^isDark)(UIColor *) = ^(UIColor *color){
 const CGFloat *component = CGColorGetComponents(color.CGColor);
 CGFloat brightness = ((component[0] * 299) + (component[1] * 587) + (component[2] * 114)) / 1000;

 if (brightness &lt; 0.75)
 return YES;
 return NO;
};
</code></pre>

blocks|key|3054444|text|下面是执行此检查的Swift+(3)扩展。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3054445|此扩展适用于灰度颜色。但是，如果您使用RGB初始化器创建所有颜色，而不使用UIColor.black和UIColor.white等内置颜色，则可以删除额外的检查。|offset|length|style|CODE|3054446|extension+UIColor+{

++++//+Check+if+the+color+is+light+or+dark,+as+defined+by+the+injected+lightness+threshold.
++++//+Some+people+report+that+0.7+is+best.+I+suggest+to+find+out+for+yourself.
++++//+A+nil+value+is+returned+if+the+lightness+couldn't+be+determined.
++++func+isLight(threshold:+Float+=+0.5)+->+Bool?+{
++++++++let+originalCGColor+=+self.cgColor

++++++++//+Now+we+need+to+convert+it+to+the+RGB+colorspace.+UIColor.white+/+UIColor.black+are+greyscale+and+not+RGB.
++++++++//+If+you+don't+do+this+then+you+will+crash+when+accessing+components+index+2+below+when+evaluating+greyscale+colors.
++++++++let+RGBCGColor+=+originalCGColor.converted(to:+CGColorSpaceCreateDeviceRGB(),+intent:+.defaultIntent,+options:+nil)
++++++++guard+let+components+=+RGBCGColor?.components+else+{
++++++++++++return+nil
++++++++}
++++++++guard+components.count+>=+3+else+{
++++++++++++return+nil
++++++++}

++++++++let+brightness+=+Float(((components[0]+*+299)+%2B+(components[1]+*+587)+%2B+(components[2]+*+114))+/+1000)
++++++++return+(brightness+>+threshold)
++++}
}|code-block|syntax|javascript|3054447|测试：|3054448|func+testItWorks()+{
++++XCTAssertTrue(UIColor.yellow.isLight()!,+"Yellow+is+LIGHT")
++++XCTAssertFalse(UIColor.black.isLight()!,+"Black+is+DARK")
++++XCTAssertTrue(UIColor.white.isLight()!,+"White+is+LIGHT")
++++XCTAssertFalse(UIColor.red.isLight()!,+"Red+is+DARK")
}|3054449|注意:已更新至Swift+3+12/7/18|BOLD|3054450|entityMap^0|0|11|D|1F|D|0|0|0|0|0|M|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|W|8|@$D|X|E|Y|F|G]|$D|Z|E|10|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|11|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|12|8|@]|9|@]|A|$]]|$1|O|3|P|5|J|7|13|8|@]|9|@]|A|$K|L]]|$1|Q|3|R|5|6|7|14|8|@$D|15|E|16|F|S]]|9|@]|A|$]]|$1|T|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|U|$]]

<h1>Here is a Swift (3) extension to perform this check.</h1>

This extension works with greyscale colors. However, if you are creating all your colors with the RGB initializer and not using the built in colors such as <code>UIColor.black</code> and <code>UIColor.white</code>, then possibly you can remove the additional checks.

<pre><code>extension UIColor {

 // Check if the color is light or dark, as defined by the injected lightness threshold.
 // Some people report that 0.7 is best. I suggest to find out for yourself.
 // A nil value is returned if the lightness couldn't be determined.
 func isLight(threshold: Float = 0.5) -&gt; Bool? {
 let originalCGColor = self.cgColor

 // Now we need to convert it to the RGB colorspace. UIColor.white / UIColor.black are greyscale and not RGB.
 // If you don't do this then you will crash when accessing components index 2 below when evaluating greyscale colors.
 let RGBCGColor = originalCGColor.converted(to: CGColorSpaceCreateDeviceRGB(), intent: .defaultIntent, options: nil)
 guard let components = RGBCGColor?.components else {
 return nil
 }
 guard components.count &gt;= 3 else {
 return nil
 }

 let brightness = Float(((components[0] * 299) + (components[1] * 587) + (components[2] * 114)) / 1000)
 return (brightness &gt; threshold)
 }
}
</code></pre>

Tests:

<pre><code>func testItWorks() {
 XCTAssertTrue(UIColor.yellow.isLight()!, "Yellow is LIGHT")
 XCTAssertFalse(UIColor.black.isLight()!, "Black is DARK")
 XCTAssertTrue(UIColor.white.isLight()!, "White is LIGHT")
 XCTAssertFalse(UIColor.red.isLight()!, "Red is DARK")
}
</code></pre>

Note: Updated to Swift 3 12/7/18

blocks|key|310659|text|我在一个类别中对这个问题的解决方案(来自这里的其他答案)。也适用于灰度颜色，在撰写本文时，其他答案都不能。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|310660|@interface+UIColor+(Ext)

++++-+(BOOL)+colorIsLight;

@end

@implementation+UIColor+(Ext)

++++-+(BOOL)+colorIsLight+{
++++++++CGFloat+colorBrightness+=+0;

++++++++CGColorSpaceRef+colorSpace+=+CGColorGetColorSpace(self.CGColor);
++++++++CGColorSpaceModel+colorSpaceModel+=+CGColorSpaceGetModel(colorSpace);

++++++++if(colorSpaceModel+==+kCGColorSpaceModelRGB){
++++++++++++const+CGFloat+*componentColors+=+CGColorGetComponents(self.CGColor);

++++++++++++colorBrightness+=+((componentColors[0]+*+299)+%2B+(componentColors[1]+*+587)+%2B+(componentColors[2]+*+114))+/+1000;
++++++++}+else+{
++++++++++++[self+getWhite:&colorBrightness+alpha:0];
++++++++}

++++++++return+(colorBrightness+>=+.5f);
++++}

@end|code-block|syntax|javascript|310661|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

My solution to this problem in a category (drawn from other answers here). Also works with grayscale colors, which at the time of writing none of the other answers do.

<pre><code>@interface UIColor (Ext)

 - (BOOL) colorIsLight;

@end

@implementation UIColor (Ext)

 - (BOOL) colorIsLight {
 CGFloat colorBrightness = 0;

 CGColorSpaceRef colorSpace = CGColorGetColorSpace(self.CGColor);
 CGColorSpaceModel colorSpaceModel = CGColorSpaceGetModel(colorSpace);

 if(colorSpaceModel == kCGColorSpaceModelRGB){
 const CGFloat *componentColors = CGColorGetComponents(self.CGColor);

 colorBrightness = ((componentColors[0] * 299) + (componentColors[1] * 587) + (componentColors[2] * 114)) / 1000;
 } else {
 [self getWhite:&amp;colorBrightness alpha:0];
 }

 return (colorBrightness &gt;= .5f);
 }

@end
</code></pre>

blocks|key|315656|text|下面的方法是在Swift语言中根据颜色中的白色来判断颜色是亮还是暗。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|315657|func+isLightColor(color:+UIColor)+->+Bool+
{
+++var+white:+CGFloat+=+0.0
+++color.getWhite(&white,+alpha:+nil)

+++var+isLight+=+false

+++if+white+>=+0.5
+++{
+++++++isLight+=+true
+++++++NSLog("color+is+light:+%25f",+white)
+++}
+++else
+++{
++++++NSLog("Color+is+dark:+%25f",+white)
+++}

+++return+isLight
}|code-block|syntax|javascript|315658|下面的方法是使用颜色分量在Swift中发现颜色是亮的还是暗的。|315659|func+isLightColor(color:+UIColor)+->+Bool+
{
+++++var+isLight+=+false

+++++var+componentColors+=+CGColorGetComponents(color.CGColor)

+++++var+colorBrightness:+CGFloat+=+((componentColors[0]+*+299)+%2B+(componentColors[1]+*+587)+%2B+(componentColors[2]+*+114))+/+1000;
+++++if+(colorBrightness+>=+0.5)
+++++{
++++++++isLight+=+true
++++++++NSLog("my+color+is+light")
+++++}
+++++else
+++++{
++++++++NSLog("my+color+is+dark")
+++++}++
+++++return+isLight
}|315660|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Following method is find color is light or dark in Swift language based on white in color.

<pre><code>func isLightColor(color: UIColor) -&gt; Bool 
{
 var white: CGFloat = 0.0
 color.getWhite(&amp;white, alpha: nil)

 var isLight = false

 if white &gt;= 0.5
 {
 isLight = true
 NSLog("color is light: %f", white)
 }
 else
 {
 NSLog("Color is dark: %f", white)
 }

 return isLight
}
</code></pre>

Following method is find color is light or dark in Swift using color components.

<pre><code>func isLightColor(color: UIColor) -&gt; Bool 
{
 var isLight = false

 var componentColors = CGColorGetComponents(color.CGColor)

 var colorBrightness: CGFloat = ((componentColors[0] * 299) + (componentColors[1] * 587) + (componentColors[2] * 114)) / 1000;
 if (colorBrightness &gt;= 0.5)
 {
 isLight = true
 NSLog("my color is light")
 }
 else
 {
 NSLog("my color is dark")
 } 
 return isLight
}
</code></pre>

blocks|key|312640|text|Swift3|type|unstyled|depth|inlineStyleRanges|entityRanges|data|312641|extension+UIColor+{
++++var+isLight:+Bool+{
++++++++var+white:+CGFloat+=+0
++++++++getWhite(&white,+alpha:+nil)
++++++++return+white+>+0.5
++++}
}

//+Usage
if+color.isLight+{
++++label.textColor+=+UIColor.black
}+else+{
++++label.textColor+=+UIColor.white
}|code-block|syntax|javascript|312642|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<h1>Swift3</h1>
<pre><code>extension UIColor {
 var isLight: Bool {
 var white: CGFloat = 0
 getWhite(&amp;white, alpha: nil)
 return white &gt; 0.5
 }
}

// Usage
if color.isLight {
 label.textColor = UIColor.black
} else {
 label.textColor = UIColor.white
}
</code></pre>

blocks|key|3054484|text|更简单的Swift+3扩展：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3054485|extension+UIColor+{
++++func+isLight()+->+Bool+{
++++++++guard+let+components+=+cgColor.components+else+{+return+false+}
++++++++let+redBrightness+=+components[0]+*+299
++++++++let+greenBrightness+=+components[1]+*+587
++++++++let+blueBrightness+=+components[2]+*+114
++++++++let+brightness+=+(redBrightness+%2B+greenBrightness+%2B+blueBrightness)+/+1000
++++++++return+brightness+>+0.5
++++}
}|code-block|syntax|javascript|3054486|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Simpler Swift 3 extension:

<pre><code>extension UIColor {
 func isLight() -&gt; Bool {
 guard let components = cgColor.components else { return false }
 let redBrightness = components[0] * 299
 let greenBrightness = components[1] * 587
 let blueBrightness = components[2] * 114
 let brightness = (redBrightness + greenBrightness + blueBrightness) / 1000
 return brightness &gt; 0.5
 }
}
</code></pre>

blocks|key|312649|text|Swift+4版本|type|unstyled|depth|inlineStyleRanges|entityRanges|data|312650|extension+UIColor+{
++++func+isLight()+->+Bool+{
++++++++guard+let+components+=+cgColor.components,+components.count+>+2+else+{return+false}
++++++++let+brightness+=+((components[0]+*+299)+%2B+(components[1]+*+587)+%2B+(components[2]+*+114))+/+1000
++++++++return+(brightness+>+0.5)
++++}
}|code-block|syntax|javascript|312651|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Swift 4 Version

<pre><code>extension UIColor {
 func isLight() -&gt; Bool {
 guard let components = cgColor.components, components.count &gt; 2 else {return false}
 let brightness = ((components[0] * 299) + (components[1] * 587) + (components[2] * 114)) / 1000
 return (brightness &gt; 0.5)
 }
}
</code></pre>

blocks|key|3268098|text|对于我来说，只使用CGColorGetComponents是行不通的，我为UIColors得到了两个组件，比如白色。所以我得先检查一下spaceModel的颜色。这就是我想出来的，最终成为@mattsven答案的快速版本。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3268099|色彩空间取自：https://stackoverflow.com/a/16981916/4905076|offset|length|3268100|extension+UIColor+{
++++func+isLight()+->+Bool+{
++++++++if+let+colorSpace+=+self.cgColor.colorSpace+{
++++++++++++if+colorSpace.model+==+.rgb+{
++++++++++++++++guard+let+components+=+cgColor.components,+components.count+>+2+else+{return+false}

++++++++++++++++let+brightness+=+((components[0]+*+299)+%2B+(components[1]+*+587)+%2B+(components[2]+*+114))+/+1000

++++++++++++++++return+(brightness+>+0.5)
++++++++++++}
++++++++++++else+{
++++++++++++++++var+white+:+CGFloat+=+0.0

++++++++++++++++self.getWhite(&white,+alpha:+nil)

++++++++++++++++return+white+>=+0.5
++++++++++++}
++++++++}

++++++++return+false
++++}|code-block|syntax|javascript|3268101|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/16981916/4905076^0|0|7|18|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@$D|U|E|V|1|W]]|A|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

For me using only CGColorGetComponents didn't worked, I get 2 components for UIColors like white. So I have to check the color spaceModel first.
This is what I came up with that ended up being the swift version of @mattsven's answer.

Color space taken from here: <a href="https://stackoverflow.com/a/16981916/4905076">https://stackoverflow.com/a/16981916/4905076</a>

<pre><code>extension UIColor {
 func isLight() -&gt; Bool {
 if let colorSpace = self.cgColor.colorSpace {
 if colorSpace.model == .rgb {
 guard let components = cgColor.components, components.count &gt; 2 else {return false}

 let brightness = ((components[0] * 299) + (components[1] * 587) + (components[2] * 114)) / 1000

 return (brightness &gt; 0.5)
 }
 else {
 var white : CGFloat = 0.0

 self.getWhite(&amp;white, alpha: nil)

 return white &gt;= 0.5
 }
 }

 return false
 }
</code></pre>

blocks|key|310686|text|UIColor有以下方法可以转换为HSB色彩空间|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|310687|-+(BOOL)getHue:(CGFloat+*)hue+saturation:(CGFloat+*)saturation+brightness:(CGFloat+*)brightness+alpha:(CGFloat+*)alpha;|code-block|syntax|javascript|310688|entityMap^0|H|7|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

UIColor has the following method to convert to HSB color space:

<pre><code>- (BOOL)getHue:(CGFloat *)hue saturation:(CGFloat *)saturation brightness:(CGFloat *)brightness alpha:(CGFloat *)alpha;
</code></pre>

I need to determine whether a selected UIColor (picked by the user) is dark or bright, so I can change the color of a line of text that sits on top of that color, for better readability.

Here's an example in Flash/Actionscript (with demo):
<a href="http://web.archive.org/web/20100102024448/http://theflashblog.com/?p=173" rel="noreferrer">http://web.archive.org/web/20100102024448/http://theflashblog.com/?p=173</a>

Any thoughts?

Cheers,
Andre

UPDATE

Thanks to everyone's suggestions, here's the working code:

<pre><code>- (void) updateColor:(UIColor *) newColor
{
 const CGFloat *componentColors = CGColorGetComponents(newColor.CGColor);

 CGFloat colorBrightness = ((componentColors[0] * 299) + (componentColors[1] * 587) + (componentColors[2] * 114)) / 1000;
 if (colorBrightness &lt; 0.5)
 {
 NSLog(@"my color is dark");
 }
 else
 {
 NSLog(@"my color is light");
 }
}
</code></pre>

Thanks once again :)

Check if UIColor is dark or bright?

Swift

我需要确定选定的UIColor (由用户选择)是暗的还是亮的，这样我就可以更改位于该颜色之上的一行文本的颜色，以获得更好的可读性。下面是一个用Flash/Actionscript编写的例子(带演示)：有什么想法吗？干杯，安德烈更新感谢大家的建议，下面是工作代码：- (void) updateColor:(UIColor...

问检查UIColor是暗的还是亮的？
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