Face redaction in document using Swift for iOS

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//
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//  Copyright © 2020-2026 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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final class FaceRedactionExample: Example {
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    // MARK: Lifecycle
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    override init() {
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        super.init()
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        title = "Face Redaction"
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        contentDescription = "Shows how to redact faces in documents with PSPDFProcessor."
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        category = .documentProcessing
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        priority = 12
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
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        let document = AssetLoader.document(for: "Flight Attendants.pdf")
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        // If there are any existing redact annotations, remove them.
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        for pageIndex in 0..<document.pageCount {
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            let existingRedactAnnotations = document.annotationsForPage(at: pageIndex, type: .redaction)
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            document.remove(annotations: existingRedactAnnotations)
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        }
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        let status = StatusHUDItem.indeterminateProgress(withText: "Detecting faces...")
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        status.setHUDStyle(.black)
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        status.push(animated: true, on: delegate.currentViewController?.view.window, completion: nil)
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        // Prepare a face detector. As this is an expensive operation, try to reuse this instance as much as possible.
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        #if targetEnvironment(simulator)
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        // `CIDetectors` don't work with high accuracy in simulators for some reason.
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        // A similar problem is described here https://developer.apple.com/forums/thread/722685,
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        // but there's no solution aside from forcing the low accuracy on simulators for now
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        let options = [CIDetectorAccuracy: CIDetectorAccuracyLow]
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        #else
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        let options = [CIDetectorAccuracy: CIDetectorAccuracyHigh]
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        #endif
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        let faceDetector = CIDetector(ofType: CIDetectorTypeFace, context: nil, options: options)!
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        // Perform this expensive work on a background queue.
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        DispatchQueue.global(qos: .background).async {
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            var documentRedactionAnnotations: [RedactionAnnotation] = []
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            for pageIndex in 0..<document.pageCount {
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                // Render this page. For efficiency, we can work with a scaled page render and still get good results.
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                let scaleFactor: CGFloat = 1 / 3.0
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                let pageSize = document.pageInfoForPage(at: pageIndex)!.size
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                let scaledPageSize = CGSize(width: pageSize.width * scaleFactor, height: pageSize.height * scaleFactor)
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                let renderedPage = try! document.imageForPage(at: pageIndex, size: scaledPageSize, clippedTo: .zero, annotations: nil, options: nil)
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                // Detect faces on the rendered page.
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                let ciImage = CIImage(cgImage: renderedPage.cgImage!)
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                let transform = CGAffineTransform(scaleX: 1 / (scaleFactor * renderedPage.scale), y: 1 / (scaleFactor * renderedPage.scale))
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                let faces = faceDetector.features(in: ciImage, options: nil)
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                // Place a redaction annotation on top of each detected face.
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                let redactionAnnotations = faces.map { face -> RedactionAnnotation in
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                    let faceBounds = face.bounds.applying(transform)
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                    let redaction = RedactionAnnotation()
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                    redaction.boundingBox = faceBounds
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                    redaction.rects = [faceBounds]
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                    redaction.color = .orange
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                    redaction.fillColor = .black
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                    redaction.outlineColor = .green
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                    redaction.pageIndex = pageIndex
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                    return redaction
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                }
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                documentRedactionAnnotations.append(contentsOf: redactionAnnotations)
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            }
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            // Add the detected redaction annotations on the main queue and hide the progress window.
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            DispatchQueue.main.async {
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                document.add(annotations: documentRedactionAnnotations)
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                let statusDone = StatusHUDItem.success(withText: "Done")
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                statusDone.pushAndPop(withDelay: 1, animated: true, on: delegate.currentViewController?.view.window)
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                status.pop(animated: true)
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            }
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        }
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        return FaceRedactionPDFViewController(document: document)
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    }
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    final class FaceRedactionPDFViewController: PDFViewController {
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        override func commonInit(with document: Document?, configuration: PDFConfiguration) {
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            super.commonInit(with: document, configuration: configuration)
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            let redactButton = UIBarButtonItem(title: "Redact", style: .plain, target: self, action: #selector(applyRedactions))
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            navigationItem.setRightBarButtonItems([annotationButtonItem, activityButtonItem, outlineButtonItem, redactButton], for: .document, animated: false)
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        }
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        @objc func applyRedactions() {
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            let processorConfiguration = Processor.Configuration(document: document)!
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            processorConfiguration.applyRedactions()
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            let redactedDocumentURL = FileHelper.temporaryPDFFileURL(prefix: "redacted")
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            let processor = Processor(configuration: processorConfiguration, securityOptions: nil)
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            try! processor.write(toFileURL: redactedDocumentURL)
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            self.document = Document(url: redactedDocumentURL)
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        }
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    }
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}