问题
Title pretty much asks it all...
I'm playing with the iOS8 Visual Effect View with Blur. It's over a UIImageView that shows a user choosable background photo. The view placed in the contentView itself is my own custom view, shows a sort of graph/calendar. Most of said calendar graph is transparent. The blur it applies to the photo behind it is really heavy. I'd like to let more of the detail leak through. But Apple only seems to give three canned values:
typedef enum {
UIBlurEffectStyleExtraLight,
UIBlurEffectStyleLight,
UIBlurEffectStyleDark
} UIBlurEffectStyle;
I've monkied around with different alphas and background colors of the UIVisualEffectView (even though the documentation warns against that), but that doesn't do anything but make it worse.
回答1:
The reason you're getting heavy blur is that the blur effect style affects the brightness level of the image, not the amount of blur applied.
Unfortunately, although Apple clearly has the ability to control the amount of blur applied programmatically--try dragging down slowly on the launchpad to watch the Spotlight blurring transition--I don't see any public API to pass a blur amount to UIBlurEffect.
This post claims that adjusting the background color alpha will drive the blur amount. It's worth a try, but I don't see where that is documented: How to fade a UIVisualEffectView and/or UIBlurEffect in and out?
回答2:
It's a pity that Apple did not provide any options for blur effect. But this workaround worked for me - animating the blur effect and pausing it before completion.
func blurEffectView(enable enable: Bool) {
let enabled = self.blurView.effect != nil
guard enable != enabled else { return }
switch enable {
case true:
let blurEffect = UIBlurEffect(style: .ExtraLight)
UIView.animateWithDuration(1.5) {
self.blurView.effect = blurEffect
}
self.blurView.pauseAnimation(delay: 0.3)
case false:
self.blurView.resumeAnimation()
UIView.animateWithDuration(0.1) {
self.blurView.effect = nil
}
}
}
and the UIView extensions for pausing (with a delay) and resuming view's animation
extension UIView {
public func pauseAnimation(delay delay: Double) {
let time = delay + CFAbsoluteTimeGetCurrent()
let timer = CFRunLoopTimerCreateWithHandler(kCFAllocatorDefault, time, 0, 0, 0, { timer in
let layer = self.layer
let pausedTime = layer.convertTime(CACurrentMediaTime(), fromLayer: nil)
layer.speed = 0.0
layer.timeOffset = pausedTime
})
CFRunLoopAddTimer(CFRunLoopGetCurrent(), timer, kCFRunLoopCommonModes)
}
public func resumeAnimation() {
let pausedTime = layer.timeOffset
layer.speed = 1.0
layer.timeOffset = 0.0
layer.beginTime = layer.convertTime(CACurrentMediaTime(), fromLayer: nil) - pausedTime
}
}
回答3:
This works for me.
I put UIVisualEffectView in an UIView before add to my view.
I make this function to use easier. You can use this function to make blur any area in your view.
func addBlurArea(area: CGRect, style: UIBlurEffectStyle) {
let effect = UIBlurEffect(style: style)
let blurView = UIVisualEffectView(effect: effect)
let container = UIView(frame: area)
blurView.frame = CGRect(x: 0, y: 0, width: area.width, height: area.height)
container.addSubview(blurView)
container.alpha = 0.8
self.view.insertSubview(container, atIndex: 1)
}
For example, you can make blur all of your view by calling:
addBlurArea(self.view.frame, style: UIBlurEffectStyle.Dark)
You can change Dark to your desired blur style and 0.8 to your desired alpha value
回答4:
You can add a UIBlurEffect over the image. And that will do the trick.
Here is an example of a UIImageView with blur effect on it. Remember to add a Image to the UIImageView.
Adjust blur amount with blurEffectView.alpha = 0.8 (from 0 to 1)
import UIKit
class BlurEffectImageView: UIImageView {
override func awakeFromNib() {
super.awakeFromNib()
addBlurEffect()
}
private func addBlurEffect(){
let blurEffect = UIBlurEffect(style: .light)
let blurEffectView = UIVisualEffectView(effect: blurEffect)
blurEffectView.alpha = 0.8
blurEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
blurEffectView.translatesAutoresizingMaskIntoConstraints = false
addSubview(blurEffectView)
NSLayoutConstraint(item: blurEffectView, attribute: .centerX, relatedBy: .equal, toItem: self, attribute: .centerX, multiplier: 1.0, constant: 0).isActive = true
NSLayoutConstraint(item: blurEffectView, attribute: .centerY, relatedBy: .equal, toItem: self, attribute: .centerY, multiplier: 1.0, constant: 0).isActive = true
NSLayoutConstraint(item: blurEffectView, attribute: .height, relatedBy: .equal, toItem: self, attribute: .height, multiplier: 1.0, constant: 0).isActive = true
NSLayoutConstraint(item: blurEffectView, attribute: .width, relatedBy: .equal, toItem: self, attribute: .width, multiplier: 1.0, constant: 0).isActive = true
}
}
回答5:
A solution similar to some here, but simpler, is to use a UIViewPropertyAnimator (iOS 10+) and set its fractionComplete property to some value between 0 and 1.
// add blur view to image view
let imgBlur = UIVisualEffectView()
imgView.addSubview(imgBlur)
imgBlur.frame = imgView.bounds
// create animator to control blur strength
let imgBlurAnimator = UIViewPropertyAnimator()
imgBlurAnimator.addAnimations {
imgBlur.effect = UIBlurEffect(style: .dark)
}
// 50% blur
imgBlurAnimator.fractionComplete = 0.5
Note, if you plan to vary fractionComplete based on a pan gesture, scroll view, slider, etc. you'll want to set pausesOnCompletion = true (iOS 11+).
回答6:
Add a BlurEffectView to a view with view's alpha < 1
func addBlurEffectView() -> Void {
if !UIAccessibilityIsReduceTransparencyEnabled() {
let viewContainer = UIView()
viewContainer.frame = self.view.bounds
viewContainer.alpha = 0.5
let blurEffect = UIBlurEffect(style: .dark)
let blurEffectView = UIVisualEffectView(effect: blurEffect)
blurEffectView.layer.zPosition = -0.5;
blurEffectView.frame = self.view.bounds;
blurEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
viewContainer.addSubview(blurEffectView)
self.view.addSubview(viewContainer)
self.view.sendSubview(toBack: viewContainer)
}
}
回答7:
I use UIVisualEffectView like this to get adjustable blur circles. The blur level is controlled by a slider that controls the alpha. I'll include the slider handler below too. The blur circle size is adjustable with pinch spread action. I will include that too. And you can drag around the blur circles. I'll leave that as an exercise for the reader. If you want a blur rectangle, just don't round the corners. To see this blur circle design in action, load the MemeSoEasy app (free), add a photo (that you can put a blur circle on top of), then add a blur circle.
UIVisualEffectView *blurVisualEffectView;
UIVisualEffect *blurEffect;
blurEffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleLight];
blurVisualEffectView = [[UIVisualEffectView alloc] initWithEffect:blurEffect];
blurVisualEffectView.frame = lastChosenBlurCircleRect;
blurVisualEffectView.center = CGPointMake(halfScreenX, halfScreenY);
[self.view addSubview:blurVisualEffectView];
CGFloat blurCornerRadius = blurVisualEffectView.bounds.size.width/2;
[[blurVisualEffectView layer]setCornerRadius:blurCornerRadius];
[[blurVisualEffectView layer]setMasksToBounds:YES];
[[blurVisualEffectView layer] setBorderWidth:4.0f];
[[blurVisualEffectView layer] setBorderColor:[UIColor blueColor].CGColor];
blurVisualEffectView.userInteractionEnabled = NO;
blurVisualEffectView.alpha = 0.97;
[blurArray addObject:blurVisualEffectView];
Slider handler :
Note that I store my blur objects in an array, so I can let users create as many as desired. The slider handler works on the last object in the array. The slider min and max values are 0.0 and 1.0
UISlider *slider_ = (UISlider *)sender;
CGFloat ourSliderValue = slider_.value;
UIVisualEffectView *currentBlurObject =
[blurArray objectAtIndex:blurArray.count - 1];
currentBlurObject.alpha = ourSliderValue;
Size change handler for pinch spread
int changeInWidth = 0; // one pixel at a time
if (pinchGesture.scale > 1.0) {
changeInWidth++;
}
if (pinchGesture.scale < 1.0) {
changeInWidth--;
}
UIVisualEffectView *currentBlurObject =
[blurArray objectAtIndex:blurArray.count - 1];
CGPoint oldCenter = currentBlurObject.center;
currentBlurObject.frame = CGRectMake(0, 0, currentBlurObject.frame.size.width + changeInWidth, currentBlurObject.frame.size.width + changeInWidth);
currentBlurObject.center = oldCenter;
lastChosenBlurCircleRect = currentBlurObject.frame;
CGFloat blurCornerRadius = currentBlurObject.frame.size.width/2;
[[currentBlurObject layer]setCornerRadius:blurCornerRadius];
回答8:
This answer is based on Mitja Semolic's excellent earlier answer. I've converted it to swift 3, added an explanation to what's happening in coments, made it an extension of a UIViewController so any VC can call it at will, added an unblurred view to show selective application, and added a completion block so that the calling view controller can do whatever it wants at the completion of the blur.
import UIKit
//This extension implements a blur to the entire screen, puts up a HUD and then waits and dismisses the view.
extension UIViewController {
func blurAndShowHUD(duration: Double, message: String, completion: @escaping () -> Void) { //with completion block
//1. Create the blur effect & the view it will occupy
let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.light)
let blurEffectView = UIVisualEffectView()//(effect: blurEffect)
blurEffectView.frame = self.view.bounds
blurEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
//2. Add the effect view to the main view
self.view.addSubview(blurEffectView)
//3. Create the hud and add it to the main view
let hud = HudView.getHUD(view: self.view, withMessage: message)
self.view.addSubview(hud)
//4. Begin applying the blur effect to the effect view
UIView.animate(withDuration: 0.01, animations: {
blurEffectView.effect = blurEffect
})
//5. Halt the blur effects application to achieve the desired blur radius
self.view.pauseAnimationsInThisView(delay: 0.004)
//6. Remove the view (& the HUD) after the completion of the duration
DispatchQueue.main.asyncAfter(deadline: .now() + duration) {
blurEffectView.removeFromSuperview()
hud.removeFromSuperview()
self.view.resumeAnimationsInThisView()
completion()
}
}
}
extension UIView {
public func pauseAnimationsInThisView(delay: Double) {
let time = delay + CFAbsoluteTimeGetCurrent()
let timer = CFRunLoopTimerCreateWithHandler(kCFAllocatorDefault, time, 0, 0, 0, { timer in
let layer = self.layer
let pausedTime = layer.convertTime(CACurrentMediaTime(), from: nil)
layer.speed = 0.0
layer.timeOffset = pausedTime
})
CFRunLoopAddTimer(CFRunLoopGetCurrent(), timer, CFRunLoopMode.commonModes)
}
public func resumeAnimationsInThisView() {
let pausedTime = layer.timeOffset
layer.speed = 1.0
layer.timeOffset = 0.0
layer.beginTime = layer.convertTime(CACurrentMediaTime(), from: nil) - pausedTime
}
}
I've confirmed that it works with both iOS 10.3.1 and iOS 11
回答9:
In order to use blur with level of blur - use my extension below:
public extension UIView {
func applyBlur(level: CGFloat) {
let context = CIContext(options: nil)
self.makeBlurredImage(with: level, context: context, completed: { processedImage in
let imageView = UIImageView(image: processedImage)
imageView.translatesAutoresizingMaskIntoConstraints = false
self.addSubview(imageView)
NSLayoutConstraint.activate([
imageView.topAnchor.constraint(equalTo: self.topAnchor),
imageView.leadingAnchor.constraint(equalTo: self.leadingAnchor),
imageView.trailingAnchor.constraint(equalTo: self.trailingAnchor),
imageView.bottomAnchor.constraint(equalTo: self.bottomAnchor),
])
})
}
private func makeBlurredImage(with level: CGFloat, context: CIContext, completed: @escaping (UIImage) -> Void) {
// screen shot
UIGraphicsBeginImageContextWithOptions(self.frame.size, false, 1)
self.layer.render(in: UIGraphicsGetCurrentContext()!)
let resultImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
let beginImage = CIImage(image: resultImage)
// make blur
let blurFilter = CIFilter(name: "CIGaussianBlur")!
blurFilter.setValue(beginImage, forKey: kCIInputImageKey)
blurFilter.setValue(level, forKey: kCIInputRadiusKey)
// extend source image na apply blur to it
let cropFilter = CIFilter(name: "CICrop")!
cropFilter.setValue(blurFilter.outputImage, forKey: kCIInputImageKey)
cropFilter.setValue(CIVector(cgRect: beginImage!.extent), forKey: "inputRectangle")
let output = cropFilter.outputImage
var cgimg: CGImage?
var extent: CGRect?
let global = DispatchQueue.global(qos: .userInteractive)
global.async {
extent = output!.extent
cgimg = context.createCGImage(output!, from: extent!)!
let processedImage = UIImage(cgImage: cgimg!)
DispatchQueue.main.async {
completed(processedImage)
}
}
}
}
How to use. Run it when frame if view already done. For example in viewDidAppear:
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
myView.applyBlur(level: 5)
}
来源：https://stackoverflow.com/questions/29498884/less-blur-with-visual-effect-view-with-blur