ios 在 UIImageView 上添加不透明度为 0.3 的黑色叠加层
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adding black overlay with 0.3 opacity over UIImageView
提问by xonegirlz
I have a UIImageView and I wanted to add a black overlay on top of it. What is the best way of doing this without having to override drawRect? I was thinking of adding a CALayer on top of it. But unsure how to get a black CALayer with a .3 alpha.
我有一个 UIImageView，我想在它上面添加一个黑色覆盖层。在不必覆盖 drawRect 的情况下这样做的最佳方法是什么？我想在它上面添加一个 CALayer。但不确定如何获得 0.3 alpha 的黑色 CALayer。
回答by Mick MacCallum
Something like this?
像这样的东西？
UIView *overlay = [[UIView alloc] initWithFrame:CGRectMake(0, 0, myImageView.frame.size.width, myImageView.frame.size.height / 2)];
[overlay setBackgroundColor:[UIColor colorWithRed:0 green:0 blue:0 alpha:0.3]];
[myImageView addSubview:overlay];
回答by swiftBoy
Thanks to Mick MacCallum
感谢米克·麦卡勒姆
Swift 3Version
斯威夫特 3版本
let overlay: UIView = UIView(frame: CGRect(x: 0, y: 0, width: cell.imageView.frame.size.width, height: cell.imageView.frame.size.height))
overlay.backgroundColor = UIColor(red: 0/255, green: 0/255, blue: 0/255, alpha: 0.1)
cell.imageView.addSubview(overlay)
I have used for Swift 2.2
我已经用于Swift 2.2
let overlay: UIView = UIView(frame: CGRectMake(0, 0, cell.imageView.frame.size.width, cell.imageView.frame.size.height))
overlay.backgroundColor = UIColor(red: 0/255, green: 0/255, blue: 0/255, alpha: 0.1)
cell.imageView.addSubview(overlay)
回答by nfarshchi
The MDT answer is correct. This is just another way to use a CAGradientLayerbeside of UIView. I think it will make what you want with more graphical options.
MDT 答案是正确的。这只是另一种方式来使用CAGradientLayer的旁边UIView。我认为它将通过更多的图形选项满足您的需求。
first you should add
首先你应该添加
#import <QuartzCore/QuartzCore.h>
to your ViewController.mand any place that you want to add this overlay to your UIImageuse:
到您ViewController.m和您想要将此叠加层添加到您的UIImage用途的任何地方：
CAGradientLayer *gradientLayer = [CAGradientLayer layer];
gradientLayer.frame = myImageView.layer.bounds;
gradientLayer.colors = [NSArray arrayWithObjects:
(id)[UIColor colorWithWhite:0.9f alpha:0.7f].CGColor,
(id)[UIColor colorWithWhite:0.0f alpha:0.3f].CGColor,
nil];
gradientLayer.locations = [NSArray arrayWithObjects:
[NSNumber numberWithFloat:0.0f],
[NSNumber numberWithFloat:0.5f],
nil];
//If you want to have a border for this layer also
gradientLayer.borderColor = [UIColor colorWithWhite:1.0f alpha:1.0f].CGColor;
gradientLayer.borderWidth = 1;
[myImageView.layer addSublayer:gradientLayer];
I hope this will help you make it
我希望这会帮助你做到
回答by pasawaya
This is similar to MDT's answer except using CALayer properties:
除了使用 CALayer 属性外，这类似于 MDT 的答案：
UIView *blackOverlay = [[UIView alloc] initWithFrame: imageView.frame];
blackOverlay.layer.backgroundColor = [[UIColor blackColor] CGColor];
blackOverlay.layer.opacity = 0.3f;
[self.view addSubview: blackOverlay];
回答by DrummerB
Did you think about adding a UIViewwith black backgroundColor and 0.3 alpha as a subview to the image view?
你有没有想过UIView在图像视图中添加一个带有黑色背景颜色和 0.3 alpha 的子视图？
