ios 调整 UIColor 的 alpha
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Adjust alpha of UIColor
提问by Eric
I set a UIColorusing rgb to a background of a UILabel. I'm trying to adjust the alphaonly. How can I modify the alpha of an existing rgb UIColor?
我将 a UIColorusing rgb设置为 a 的背景UILabel。我正在尝试调整alpha唯一的。如何修改现有 rgb 的 alpha 值UIColor？
Edit
编辑
Basically I have UILabelsthat have a set UIColor(using rgb), and I won't know what color the UILabelsare. At a certain point, I will have to change the labelsalpha`. How can I just change the labels color alpha?
基本上我UILabels有一套UIColor（使用 rgb），我不知道它们是什么颜色UILabels。在某个时候，我将不得不更改labelsalpha`。我怎样才能改变标签颜色 alpha？
回答by Eric
colorWithAlphaComponent:did the trick.
colorWithAlphaComponent:成功了。
So what I had to do was:
所以我必须做的是：
self.mylabel.backgroundColor = [self.myLabel.backgroundColor colorWithAlphaComponent:0.3];
回答by GraSim
Swift 3 & 4
斯威夫特 3 & 4
yourUIView.backgroundColor = UIColor.white.withAlphaComponent(0.75)
Swift 2
斯威夫特 2
yourUIView.backgroundColor = UIColor.whiteColor().colorWithAlphaComponent(0.75)
回答by chris g
If you have custom colors defined, you can do this as well:
如果您定义了自定义颜色，您也可以这样做：
view.backgroundColor = [[MyClass someColor] colorWithAlphaComponent:0.25];
回答by JZAU
why not using label.alpha = 0.5? to adjust your label's alpha?
为什么不使用label.alpha = 0.5？调整标签的alpha？
update: if you want to adjust alpha from a old color, here is an example:
更新：如果您想从旧颜色调整 alpha，这是一个示例：
UIColor uicolor = [UIColor greenColor];
CGColorRef color = [uicolor CGColor];
int numComponents = CGColorGetNumberOfComponents(color);
UIColor newColor;
if (numComponents == 4)
{
const CGFloat *components = CGColorGetComponents(color);
CGFloat red = components[0];
CGFloat green = components[1];
CGFloat blue = components[2];
newColor = [UIColor colorWithRed: red green: green blue: blue alpha: YOURNEWALPHA];
}
回答by Santu C
Please set alpha in below code -
请在下面的代码中设置 alpha -
[UIColor colorWithRed:200.0/255.0 green:191.0/255.0 blue:231.0 /255.0 alpha:1.0]
