How to Edit the Uiblureffect Intensity

How to edit the UIBlurEffect intensity?

Adjusting the blur itself is not possible... But, you can adjust how visible the blur view is. This can be done in a number of ways, only three of which I can think of at the moment:

1st Option: Adjust the alpha of your UIVisualEffectView instance e.g:

effectView.alpha = 0.4f;

2nd Option: Add a UIView instance to effectView at Index 0 and adjust the alpha of this UIView instance. e.g:

UIView *blurDilutionView = [[UIView alloc] initWithFrame: effectView.frame];
blurDilutionView.backgroundColor = [[UIColor whiteColor] colorWithAlphaComponent: 0.5];
blurDilutionView.autoresizingMask = UIViewAutoresizingFlexibleTopMargin|UIViewAutoresizingFlexibleBottomMargin|UIViewAutoresizingFlexibleWidth|UIViewAutoresizingFlexibleHeight;//if not using AutoLayout
[effectView insertSubview:blurDilutionView atIndex:0];

3rd Option: use multiple UIVisualEffectView instances (I have not tried this yet, more of an idea). Apply an alpha of 0.1f on each. The more UIVisualEffectView views you have the more blurry the overall look. Once again, I have not tried this option yet!

Update:
As Axeva mentioned in the comments, Apple advises against adjusting the alpha to change the blur. So use these suggestions at your own potential peril.

tweak intensity of blur effect inside UIVisualEffectView in Swift

Since there is no other parameter in UIBlurEffect , I think the only way is to use the CIFilter preset CIGaussianBlur to blur the background View and use its key inputRadius to adjust the level.

If you want to achieve the same effect as so called light/dark/ExtraLight, you can compose this filter with other filters.

How can blurriness of UIVisualEffectView be modified while dragging in iOS?

There is a way :)

As you've noticed, you can animate from a nil effect to an effect like UIBlurEffectStyleDark so if we add an animation and then pause the layer's animations we can control the progress of the effect by adjusting the layer's timeOffset!

- (void) setupBlur {
    // Setup the blur to start with no effect
    self.blurredEffectView = [[UIVisualEffectView alloc] initWithEffect:nil];

    // Add animation to desired blur effect
    [UIView animateWithDuration:1.0 animations:^{
        [self.blurredEffectView setEffect:[UIBlurEffect effectWithStyle:UIBlurEffectStyleDark]];
    }];

    // Pause layer animations
    self.blurredEffectView.layer.speed = 0;
}

Adjust blur between 0.0 and 1.0 (animation duration):

- (void) adjustBlur:(CGFloat)blurIntensity {
    self.blurredEffectView.layer.timeOffset = blurIntensity;
}

• Note: this won't work on iOS 8 where UIBlurEffect animations aren't supported.

How to fade a UIVisualEffectView and/or UIBlurEffect in and out?

I think this is new in iOS9, but you can now set the effect of a UIVisualEffectView inside an animation block:

let overlay = UIVisualEffectView()
// Put it somewhere, give it a frame...
UIView.animate(withDuration: 0.5) {
    overlay.effect = UIBlurEffect(style: .light)
}

Set it to nil to remove.

VERY IMPORTANT - When testing this on the simulator, make sure to set your simulator's Graphics Quality Override to High Quality in order for this to work.

Less Blur with `Visual Effect View with Blur`?

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?

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