Adjust NSVisualEffectView blur radius and transparency

Question

Is it possible to adjust the blur radius and transparency of an NSVisualEffectView when it's applied to an NSWindow (Swift or Objective-C)? I tried all variations of NSVisualEffectMaterial (dark, medium, light) - but that's not cutting it. In the image below I've used Apple's non-public API with CGSSetWindowBackgroundBlurRadius on the left, and NSVisualEffectView on the right.

I'm trying to achieve the look of what's on the left, but it seems I'm relegated to use the methods of the right.

Here's my code:

blurView.blendingMode = NSVisualEffectBlendingMode.BehindWindow
blurView.material = NSVisualEffectMaterial.Medium
blurView.state = NSVisualEffectState.Active
self.window!.contentView!.addSubview(blurView)

Possibly, related - but doesn't answer my question:

OS X NSVisualEffect decrease blur radius? - no answer

score 3 · Answer 1 · answered May 15 '16 at 03:24

Although I wouldn't recommend this unless you are ready to fall back to it not working in a future release, you can subclass NSVisualEffectView with the following to do what you want:

- (void)updateLayer
{
    [super updateLayer];

    [CATransaction begin];
    [CATransaction setDisableActions:YES];

    CALayer *backdropLayer = self.layer.sublayers.firstObject;

    if ([backdropLayer.name hasPrefix:@"kCUIVariantMac"]) {
        for (CALayer *activeLayer in backdropLayer.sublayers) {
            if ([activeLayer.name isEqualToString:@"Active"]) {
                for (CALayer *sublayer in activeLayer.sublayers) {
                    if ([sublayer.name isEqualToString:@"Backdrop"]) {
                        for (id filter in sublayer.filters) {
                            if ([filter respondsToSelector:@selector(name)] && [[filter name] isEqualToString:@"blur"]) {
                                if ([filter respondsToSelector:@selector(setValue:forKey:)]) {
                                    [filter setValue:@5 forKey:@"inputRadius"];
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    [CATransaction commit];
}

Although this doesn't use Private APIs per se, it does start to dig into layer hierarchies which you do not own, so be sure to double check that what you are getting back is what you expect, and fail gracefully if not. For instance, on 10.10 Yosemite, the Backdrop layer was a direct decedent of the Visual Effect view, so things are likely to change in the future.

Hi, thanks for the answer, but unfortunately this doesn't seem to adjust the transparency at all. — Cocoa Puffs, May 28 '16 at 21:36
This example was for within window blurs, so you may need to poke around the layer hierarchy to get the particular layer you want. Set a breakpoint in `updateLayer`, and continuously call `po self.layer.sublayers` to see what you need to search for in your visual effect view. Conveniently, most layers are named, so you can drill down little by little like that. I believe there's another layer called `Tint` that controls the color tint as well. — Dimitri Bouniol, May 29 '16 at 18:01

AD Progress · Answer 2 · 2020-07-20T23:13:19.697

I had the same issue as you had and I have solved it with a little trick seems to do the job that I wanted. I hope that it will also help you.

So in my case, I have added the NSVisualEffectView in storyboards and set its properties as follows:

and my View hierarchy is as follows:

All that reduces the blur is in the NSViewController in:

override func viewWillAppear() {
    super.viewWillAppear()
    //Adds transparency to the app
    view.window?.isOpaque = false
    view.window?.alphaValue = 0.98 //tweak the alphaValue for your desired effect
}

Going with your example this code should work in addition with the tweak above:

    let blurView = NSVisualEffectView(frame: view.bounds)
    blurView.blendingMode = .behindWindow
    blurView.material = .fullScreenUI
    blurView.state = .active
    view.window?.contentView?.addSubview(blurView)

Swift 5 code For anyone interested here is a link to my repo where I have created a small prank app which uses the code above: GitHub link

Adjust NSVisualEffectView blur radius and transparency

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