ios 从 UIColor 创建 UIImage 以用作 UIButton 的背景图像
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Creating a UIImage from a UIColor to use as a background image for UIButton
提问by Thorsten
I'm creating a colored image like this:
我正在创建这样的彩色图像：
CGRect rect = CGRectMake(0, 0, 1, 1);
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context,
[[UIColor redColor] CGColor]);
// [[UIColor colorWithRed:222./255 green:227./255 blue: 229./255 alpha:1] CGColor]) ;
CGContextFillRect(context, rect);
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
and then use it as the background image of a button:
然后将其用作按钮的背景图像：
[resultButton setBackgroundImage:img forState:UIControlStateNormal];
This works great using the redColor, however I want to use an RGB color (as shown in the commented line). When I use the RGB color, the buttons background isn't changed.
使用 redColor 效果很好，但是我想使用 RGB 颜色（如注释行所示）。当我使用 RGB 颜色时，按钮背景不会改变。
What am I missing?
我错过了什么？
回答by ScottWasserman
I created a category around UIButton to be able to set the background color of the button and set the state. You might find this useful.
我在 UIButton 周围创建了一个类别，以便能够设置按钮的背景颜色并设置状态。您可能会发现这很有用。
@implementation UIButton (ButtonMagic)
- (void)setBackgroundColor:(UIColor *)backgroundColor forState:(UIControlState)state {
[self setBackgroundImage:[UIButton imageFromColor:backgroundColor] forState:state];
}
+ (UIImage *)imageFromColor:(UIColor *)color {
CGRect rect = CGRectMake(0, 0, 1, 1);
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, [color CGColor]);
CGContextFillRect(context, rect);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
This will be part of a set of helper categories I'm open sourcing this month.
这将是我本月开源的一组帮助程序类别的一部分。
Swift 2.2
斯威夫特 2.2
extension UIImage {
static func fromColor(color: UIColor) -> UIImage {
let rect = CGRect(x: 0, y: 0, width: 1, height: 1)
UIGraphicsBeginImageContext(rect.size)
let context = UIGraphicsGetCurrentContext()
CGContextSetFillColorWithColor(context, color.CGColor)
CGContextFillRect(context, rect)
let img = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return img
}
}
Swift 3.0
斯威夫特 3.0
extension UIImage {
static func from(color: UIColor) -> UIImage {
let rect = CGRect(x: 0, y: 0, width: 1, height: 1)
UIGraphicsBeginImageContext(rect.size)
let context = UIGraphicsGetCurrentContext()
context!.setFillColor(color.cgColor)
context!.fill(rect)
let img = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return img!
}
}
Use as
用于
let img = UIImage.from(color: .black)
回答by ben
Xamarin.iOS solution
Xamarin.iOS 解决方案
public UIImage CreateImageFromColor()
{
var imageSize = new CGSize(30, 30);
var imageSizeRectF = new CGRect(0, 0, 30, 30);
UIGraphics.BeginImageContextWithOptions(imageSize, false, 0);
var context = UIGraphics.GetCurrentContext();
var red = new CGColor(255, 0, 0);
context.SetFillColor(red);
context.FillRect(imageSizeRectF);
var image = UIGraphics.GetImageFromCurrentImageContext();
UIGraphics.EndImageContext();
return image;
}
回答by Jesse Rusak
Are you using ARC? The problem here is that you don't have a reference to the UIColorobject that you're trying to apply; the CGColoris backed by that UIColor, but ARC will deallocate the UIColorbefore you have a chance to use the CGColor.
你在使用ARC吗？这里的问题是您没有对要应用的UIColor对象的引用；在CGColor由支持UIColor，但ARC会回收UIColor你有机会使用之前CGColor。
The clearest solution is to have a local variable pointing to your UIColorwith the objc_precise_lifetimeattribute.
最明确的解决方案是让一个局部变量指向你UIColor的objc_precise_lifetime属性。
You can read more about this exact case on this article about UIColor and short ARC lifetimesor get more details about the objc_precise_lifetimeattribute.
您可以在这篇有关 UIColor 和短 ARC 生命周期的文章中阅读有关此确切案例的更多信息，或获取有关该objc_precise_lifetime属性的更多详细信息。
回答by iGerm
Add the dots to all values:
将点添加到所有值：
[[UIColor colorWithRed:222./255. green:227./255. blue: 229./255. alpha:1] CGColor]) ;
Otherwise, you are dividing float by int.
否则，您将 float 除以 int。
回答by aknew
I suppose that 255 in 227./255 is perceived as an integer and divide is always return 0
我想 227./255 中的 255 被认为是一个整数，除法总是返回 0
回答by bdunagan
Your code works fine. You can verify the RGB colors with Iconfactory's xScope. Just compare it to [UIColor whiteColor].
你的代码工作正常。您可以使用Iconfactory 的 xScope验证 RGB 颜色。只需将其与[UIColor whiteColor].
回答by Muzamil Hassan
CGContextSetFillColorWithColor(context,[[UIColor colorWithRed:(255/255.f) green:(0/255.f) blue: (0/255.f) alpha:1] CGColor]);
