Blur PDF Page in Swift for iOS

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//
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//  Copyright © 2018-2025 PSPDFKit GmbH. All rights reserved.
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//
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//  The Nutrient sample applications are licensed with a modified BSD license.
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//  Please see License for details. This notice may not be removed from this file.
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//
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import PSPDFKit
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import PSPDFKitUI
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class BlurPagesExample: Example, PDFViewControllerDelegate {
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    override init() {
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        super.init()
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        title = "Blur Pages"
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        contentDescription = "Shows how to blur specific pages in a document."
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        category = .viewCustomization
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
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        let document = AssetLoader.writableDocument(for: .welcome, overrideIfExists: false)
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        let controller = PDFViewController(document: document, delegate: self) {
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            $0.pageTransition = .scrollPerSpread
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            $0.pageMode = .single
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            $0.thumbnailBarMode = .none
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            $0.isTextSelectionEnabled = false
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        }
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        // Remove the thumbnails button item from the toolbar.
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        let rightBarButtonItems = controller.navigationItem.rightBarButtonItems?.filter({ buttonItem -> Bool in
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            return buttonItem != controller.thumbnailsButtonItem
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        })
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        controller.navigationItem.setRightBarButtonItems(rightBarButtonItems, animated: false)
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        return controller
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    }
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    internal func pdfViewController(_ pdfController: PDFViewController, willBeginDisplaying pageView: PDFPageView, forPageAt pageIndex: Int) {
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        // Only blur the first three pages.
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        if pageIndex < 2 {
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            // Blur pages if they aren't already blurred.
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            if !pageView.isBlurred {
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                let effect = UIBlurEffect(style: .light)
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                let visualEffectView = UIVisualEffectView(effect: effect)
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                visualEffectView.frame = pageView.bounds
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                visualEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
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                pageView.addSubview(visualEffectView)
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            }
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        } else {
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            // Remove the visual effect view from the blurred pages if necessary.
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            for view in pageView.subviews where view is UIVisualEffectView {
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                view.removeFromSuperview()
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            }
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        }
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    }
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}
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fileprivate extension PDFPageView {
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    var isBlurred: Bool {
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        return self.subviews.contains(where: { $0 is UIVisualEffectView })
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    }
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}