pencilkit-drawing

PencilKit Drawing Capture Apple Pencil and finger input using PKCanvasView , manage drawing tools with PKToolPicker , serialize drawings with PKDrawing , and wrap PencilKit in SwiftUI. Targets Swift 6.2 / iOS 26+. Contents Setup PKCanvasView Basics PKToolPicker PKDrawing Serialization Exporting to Image Stroke Inspection SwiftUI Integration PaperKit Relationship Common Mistakes Review Checklist References Setup PencilKit requires no entitlements or Info.plist entries. Import PencilKit and create a PKCanvasView . import PencilKit Platform availability: iOS 13+, iPadOS 13+, Mac Catalyst 13.1+, visionOS 1.0+. PKCanvasView Basics PKCanvasView is a UIScrollView subclass that captures Apple Pencil and finger input and renders strokes. import PencilKit import UIKit class DrawingViewController : UIViewController , PKCanvasViewDelegate { let canvasView = PKCanvasView ( ) override func viewDidLoad ( ) { super . viewDidLoad ( ) canvasView . delegate = self canvasView . drawingPolicy = . anyInput canvasView . tool = PKInkingTool ( . pen , color : . black , width : 5 ) canvasView . frame = view . bounds canvasView . autoresizingMask = [ . flexibleWidth , . flexibleHeight ] view . addSubview ( canvasView ) } func canvasViewDrawingDidChange ( _ canvasView : PKCanvasView ) { // Drawing changed -- save or process } } Drawing Policies Policy Behavior .default Apple Pencil draws; finger scrolls .anyInput Both pencil and finger draw .pencilOnly Only Apple Pencil draws; finger always scrolls canvasView . drawingPolicy = . pencilOnly Configuring the Canvas // Set a large drawing area (scrollable) canvasView . contentSize = CGSize ( width : 2000 , height : 3000 ) // Enable/disable the ruler canvasView . isRulerActive = true // Set the current tool programmatically canvasView . tool = PKInkingTool ( . pencil , color : . blue , width : 3 ) canvasView . tool = PKEraserTool ( . vector ) PKToolPicker PKToolPicker displays a floating palette of drawing tools. The canvas automatically adopts the selected tool. class DrawingViewController : UIViewController { let canvasView = PKCanvasView ( ) let toolPicker = PKToolPicker ( ) override func viewDidAppear ( _ animated : Bool ) { super . viewDidAppear ( animated ) toolPicker . setVisible ( true , forFirstResponder : canvasView ) toolPicker . addObserver ( canvasView ) canvasView . becomeFirstResponder ( ) } } Custom Tool Picker Items Create a tool picker with specific tools. let toolPicker = PKToolPicker ( toolItems : [ PKToolPickerInkingItem ( type : . pen , color : . black ) , PKToolPickerInkingItem ( type : . pencil , color : . gray ) , PKToolPickerInkingItem ( type : . marker , color : . yellow ) , PKToolPickerEraserItem ( type : . vector ) , PKToolPickerLassoItem ( ) , PKToolPickerRulerItem ( ) ] ) Ink Types Type Description .pen Smooth, pressure-sensitive pen .pencil Textured pencil with tilt shading .marker Semi-transparent highlighter .monoline Uniform-width pen .fountainPen Variable-width calligraphy pen .watercolor Blendable watercolor brush .crayon Textured crayon PKDrawing Serialization PKDrawing is a value type (struct) that holds all stroke data. Serialize it to Data for persistence. // Save func saveDrawing ( _ drawing : PKDrawing ) throws { let data = drawing . dataRepresentation ( ) try data . write ( to : fileURL ) } // Load func loadDrawing ( ) throws -> PKDrawing { let data = try Data ( contentsOf : fileURL ) return try PKDrawing ( data : data ) } Combining Drawings var drawing1 = PKDrawing ( ) let drawing2 = PKDrawing ( ) drawing1 . append ( drawing2 ) // Non-mutating let combined = drawing1 . appending ( drawing2 ) Transforming Drawings let scaled = drawing . transformed ( using : CGAffineTransform ( scaleX : 2 , y : 2 ) ) let translated = drawing . transformed ( using : CGAffineTransform ( translationX : 100 , y : 0 ) ) Exporting to Image Generate a UIImage from a drawing. func exportImage ( from drawing : PKDrawing , scale : CGFloat = 2.0 ) -> UIImage { drawing . image ( from : drawing . bounds , scale : scale ) } // Export a specific region let region = CGRect ( x : 0 , y : 0 , width : 500 , height : 500 ) let scale = UITraitCollection . current . displayScale let croppedImage = drawing . image ( from : region , scale : scale ) Stroke Inspection Access individual strokes, their ink, and control points. for stroke in drawing . strokes { let ink = stroke . ink print ( "Ink type: ( ink . inkType ) , color: ( ink . color ) " ) print ( "Bounds: ( stroke . renderBounds ) " ) // Access path points let path = stroke . path print ( "Points: ( path . count ) , created: ( path . creationDate ) " ) // Interpolate along the path for point in path . interpolatedPoints ( by : . distance ( 10 ) ) { print ( "Location: ( point . location ) , force: ( point . force ) " ) } } Constructing Strokes Programmatically let points = [ PKStrokePoint ( location : CGPoint ( x : 0 , y : 0 ) , timeOffset : 0 , size : CGSize ( width : 5 , height : 5 ) , opacity : 1 , force : 0.5 , azimuth : 0 , altitude : . pi / 2 ) , PKStrokePoint ( location : CGPoint ( x : 100 , y : 100 ) , timeOffset : 0.1 , size : CGSize ( width : 5 , height : 5 ) , opacity : 1 , force : 0.5 , azimuth : 0 , altitude : . pi / 2 ) ] let path = PKStrokePath ( controlPoints : points , creationDate : Date ( ) ) let stroke = PKStroke ( ink : PKInk ( . pen , color : . black ) , path : path , transform : . identity , mask : nil ) let drawing = PKDrawing ( strokes : [ stroke ] ) SwiftUI Integration Wrap PKCanvasView in a UIViewRepresentable for SwiftUI. import SwiftUI import PencilKit struct CanvasView : UIViewRepresentable { @Binding var drawing : PKDrawing @Binding var toolPickerVisible : Bool func makeUIView ( context : Context ) -> PKCanvasView { let canvas = PKCanvasView ( ) canvas . delegate = context . coordinator canvas . drawingPolicy = . anyInput canvas . drawing = drawing return canvas } func updateUIView ( _ canvas : PKCanvasView , context : Context ) { if canvas . drawing != drawing { canvas . drawing = drawing } let toolPicker = context . coordinator . toolPicker toolPicker . setVisible ( toolPickerVisible , forFirstResponder : canvas ) if toolPickerVisible { canvas . becomeFirstResponder ( ) } } func makeCoordinator ( ) -> Coordinator { Coordinator ( self ) } class Coordinator : NSObject , PKCanvasViewDelegate { let parent : CanvasView let toolPicker = PKToolPicker ( ) init ( _ parent : CanvasView ) { self . parent = parent super . init ( ) } func canvasViewDrawingDidChange ( _ canvasView : PKCanvasView ) { parent . drawing = canvasView . drawing } } } Usage in SwiftUI struct DrawingScreen : View { @State private var drawing = PKDrawing ( ) @State private var showToolPicker = true var body : some View { CanvasView ( drawing : $drawing , toolPickerVisible : $showToolPicker ) . ignoresSafeArea ( ) } } PaperKit Relationship PaperKit (iOS 26+) extends PencilKit with a complete markup experience including shapes, text boxes, images, stickers, and loupes. Use PaperKit when you need more than freeform drawing. Capability PencilKit PaperKit Freeform drawing Yes Yes Shapes & lines No Yes Text boxes No Yes Images & stickers No Yes Markup toolbar No Yes Data model PKDrawing PaperMarkup PaperKit uses PencilKit under the hood -- PaperMarkupViewController accepts PKTool for its drawingTool property and PaperMarkup can append a PKDrawing . See references/paperkit-integration.md for PaperKit patterns. Common Mistakes DON'T: Forget to call becomeFirstResponder for the tool picker The tool picker only appears when its associated responder is first responder. // WRONG: Tool picker never shows toolPicker . setVisible ( true , forFirstResponder : canvasView ) // CORRECT: Also become first responder toolPicker . setVisible ( true , forFirstResponder : canvasView ) canvasView . becomeFirstResponder ( ) DON'T: Create multiple tool pickers for the same canvas One PKToolPicker per canvas. Creating extras causes visual conflicts. // WRONG func viewDidAppear ( _ animated : Bool ) { let picker = PKToolPicker ( ) // New picker every appearance picker . setVisible ( true , forFirstResponder : canvasView ) } // CORRECT: Store picker as a property let toolPicker = PKToolPicker ( ) DON'T: Ignore content version for backward compatibility Newer ink types crash on older OS versions. Set maximumSupportedContentVersion if you need backward-compatible drawings. // WRONG: Saves a drawing with .watercolor, crashes on iOS 16 canvasView . tool = PKInkingTool ( . watercolor , color : . blue ) // CORRECT: Limit content version for compatibility canvasView . maximumSupportedContentVersion = . version2 DON'T: Compare drawings by data representation PKDrawing data is not deterministic; the same visual drawing can produce different bytes. Use equality operators instead. // WRONG if drawing1 . dataRepresentation ( ) == drawing2 . dataRepresentation ( ) { } // CORRECT if drawing1 == drawing2 { } Review Checklist PKCanvasView.drawingPolicy set appropriately ( .default for Pencil-primary apps) PKToolPicker stored as a property, not recreated each appearance canvasView.becomeFirstResponder() called to show the tool picker Drawing serialized via dataRepresentation() and loaded via PKDrawing(data:) canvasViewDrawingDidChange delegate method used to track changes maximumSupportedContentVersion set if backward compatibility needed Exported images use appropriate scale factor for the device SwiftUI wrapper avoids infinite update loops by checking drawing != binding Tool picker observer added before becoming first responder Drawing bounds checked before image export (empty drawings have .zero bounds) References Extended PencilKit patterns (advanced strokes, Scribble, delegate): references/pencilkit-patterns.md PaperKit integration patterns: references/paperkit-integration.md PencilKit framework PKCanvasView PKDrawing PKToolPicker PKInkingTool PKStroke Drawing with PencilKit Configuring the PencilKit tool picker