Create a Custom Appearance Stream Generator in Swift for iOS

1
//
2
//  Copyright © 2019-2025 PSPDFKit GmbH. All rights reserved.
3
//
4
//  The Nutrient sample applications are licensed with a modified BSD license.
5
//  Please see License for details. This notice may not be removed from this file.
6
//
7

8
import PSPDFKit
9
import PSPDFKitUI
10

11
class AppearanceStreamGeneratorWithCustomDrawingExample: Example {
12

13
    override init() {
14
        super.init()
15

16
        title = "Appearance Stream Generator with a custom drawing block"
17
        contentDescription = "Shows how to add additional custom drawing for a vector stamp annotation."
18
        category = .annotations
19
        priority = 70
20
    }
21

22
    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
23
        let document = AssetLoader.document(for: .annualReport)
24
        document.annotationSaveMode = .disabled
25
        let logoURL = AssetLoader.assetURL(for: "PSPDFKit Logo.pdf")
26
        let pageIndex: PageIndex = 0
27

28
        // Add a stamp annotation.
29
        let stampAnnotation = StampAnnotation()
30
        stampAnnotation.boundingBox = CGRect(x: 180.0, y: 150.0, width: 444.0, height: 500.0)
31
        stampAnnotation.color = UIColor(red: 0, green: 100 / 255, blue: 0, alpha: 1)
32
        stampAnnotation.fillColor = UIColor.clear
33
        stampAnnotation.alpha = 0.5
34
        stampAnnotation.lineWidth = 5
35
        stampAnnotation.pageIndex = pageIndex
36

37
        // Create the appearance stream generator and setup its drawing block.
38
        let appearanceStreamGenerator = FileAppearanceStreamGenerator(fileURL: logoURL)
39
        appearanceStreamGenerator.drawingBlock = { context in
40
            // Custom drawing: Draw a green square border around the stamp.
41
            let box = stampAnnotation.boundingBox
42
            let color = stampAnnotation.color
43
            context.saveGState()
44
            guard let colorRef = color?.cgColor else {
45
                return
46
            }
47
            context.setStrokeColor(colorRef)
48
            context.stroke(box)
49
            context.setFillColor(colorRef)
50

51
            let lineWidth = stampAnnotation.lineWidth
52
            let strokeRect: CGRect = box.insetBy(dx: lineWidth / 2.0, dy: lineWidth / 2.0)
53
            let path = CGPath(rect: strokeRect, transform: nil)
54
            context.setLineWidth(lineWidth)
55
            context.setAlpha(stampAnnotation.alpha)
56
            context.addPath(path)
57
            context.drawPath(using: .stroke)
58
            context.restoreGState()
59
        }
60

61
        // Set the annotation's appearance stream generator.
62
        stampAnnotation.appearanceStreamGenerator = appearanceStreamGenerator
63
        document.add(annotations: [stampAnnotation])
64

65
        let controller = PDFViewController(document: document)
66
        return controller
67
    }
68
}