Add Apple Pencil drawing with PKCanvasView, PKToolPicker, PKDrawing serialization/export, stroke inspection, and PencilKit/PaperKit handoffs. Use when building drawing apps, annotation features, handwriting capture, signature fields, content-version-safe ink workflows, or Apple Pencil-powered experi

PencilKit Capture Apple Pencil and finger input using PKCanvasView , manage drawing tools with PKToolPicker , serialize drawings with PKDrawing , and wrap PencilKit in SwiftUI. Contents [Setup]( setup) [Capture to Export Workflow]( capture to export workflow) [PKCanvasView Basics]( pkcanvasview basics) [PKToolPicker]( pktoolpicker) [PKDrawing Serialization]( pkdrawing serialization) [Content Version Compatibility]( content version compatibility) [Exporting to Image]( exporting to image) [Stroke Inspection]( stroke inspection) [SwiftUI Integration]( swiftui integration) [PaperKit Relationship]( paperkit relationship) [Common Mistakes]( common mistakes) [Review Checklist]( review checklist) [References]( references) Setup PencilKit requires no entitlements or Info.plist entries. Import PencilKit and create a PKCanvasView . Platform availability: iOS 13+, iPadOS 13+, Mac Catalyst 13.1+, visionOS 1.0+. Capture to Export Workflow 1. Capture: Read canvasView.drawing from canvasViewDrawingDidChange( :) ; keep the previous persisted revision until the new revision completes the remaining checkpoints. 2. Serialize: Create dataRepresentation() , write atomically, and run the [decode validate/fix/retry loop]( decode validatefixretry loop). Do not mark bytes valid when PKDrawing(data:) still throws. 3. Version gate: Apply [Content Version Compatibility]( content version compatibility) before editable sync. If the recipient cannot load the drawing, preserve the full fidelity source and use an existing compatible fallback or read only preview. 4. Sync: Send only validated, compatible data and mark the revision synced after acknowledgement. On transport or conflict failure, retain the pending revision, resolve the cause, and retry without discarding the last good copy. 5. Export: Validate a nonempty drawing region and intended scale before calling image(from:scale:) ; skip export on invalid bounds without altering the serialized drawing. PKCanvasView Basics PKCanvasView is a UIScrollView subclass that captures Apple Pencil and finger input and renders strokes. Drawing Policies Policy Behavior .default Respects UIPencilInteraction.prefersPencilOnlyDrawing when the tool picker is visible; otherwise Pencil only .anyInput Both pencil and finger draw .pencilOnly Only Apple Pencil touches draw on the canvas Use .default for system standard Pencil primary canvases when the tool picker's drawing policy control should follow the user's Pencil preference. Use .anyInput for signature pads, whiteboards, or explicit finger drawing modes. Use .pencilOnly when finger input should never create strokes. Configuring the Canvas PKToolPicker PKToolPicker displays a floating palette of drawing tools. The canvas automatically adopts the selected tool. Custom Tool Picker Items Create a tool picker with specific tools. PKToolPicker(toolItems:) and custom tool picker item classes require iOS/iPadOS 18+, Mac Catalyst 18+, and visionOS 2+; those item classes are available on macOS starting in macOS 26. 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 .reed Reed pen (iOS/iPadOS/macOS/visionOS 26+) Content Versions Use [Content Version Compatibility]( content version compatibility) as the single version map and compatibility gate for both the canvas and tool picker. PKDrawing Serialization PKDrawing is a value type (struct) that holds all stroke data. Serialize it to Data for persistence. Decode Validate/Fix/Retry Loop For synced or user provided data: validate with PKDrawing(data:) ; on failure preserve the original bytes and fix the cause by refetching an intact revision or selecting a previously generated compatible copy; then retry the decode. Assign the drawing only after a successful retry. If recovery still fails, keep the source unchanged and show an error or available read only preview instead of suppressing the failure with try? . Combining Drawings Transforming Drawings Content Version Compatibility For sync, migration, downgrade, or cross device editing tasks, use requiredContentVersion as the compatibility gate and choose an explicit maximumSupportedContentVersion when old clients must keep editing. If a drawing requires a newer version than a recipient can load, preserve the full fidelity PKDrawing for capable clients and provide a read only preview or separate fallback instead of silently overwriting it. See [references/pencilkit patterns.md](references/pencilkit patterns.md) for the deeper compatibility table. Exporting to Image Generate a UIImage from a drawing. Stroke Inspection Access individual strokes, their ink, and control points. Constructing Strokes Programmatically Load [Constructing Strokes Programmatically](references/pencilkit patterns.md constructing strokes programmatically) only for generated ink paths; ordinary drawing and inspection do not need the advanced constructors. SwiftUI Integration Wrap PKCanvasView in a UIViewRepresentable for SwiftUI. For SwiftUI wrappers, set the input policy using the canonical [Drawing Policies]( drawing policies) table. Usage in SwiftUI PaperKit Relationship PaperKit (iOS 26+) extends PencilKit with a complete markup experience including shapes, text boxes, images, stickers, and loupes. Use the sibling paperkit skill when you need structured markup rather than only freeform drawing. Capability PencilKit PaperKit Freeform drawing Yes Yes Shapes & lines No Yes Text boxes No Yes Images & stickers No Yes Loupes No Yes Markup toolbar No Yes Markup insertion UI No MarkupEditViewController , MarkupToolbarViewController Data model PKDrawing PaperMarkup PaperKit uses PencilKit under the hood: PaperMarkupViewController accepts PKTool for its drawingTool property, and PaperMarkup can append a PKDrawing . Common Mistakes DON'T: Forget to call becomeFirstResponder for the tool picker The tool picker only appears when its associated responder is first responder. DON'T: Create multiple tool pickers for the same canvas One PKToolPicker per canvas. Creating extras causes visual conflicts. DON'T: Ignore content versions for backward compatibility Apply the [Content Version Compatibility]( content version compatibility) gate to both the canvas and tool picker before syncing editable drawings. DON'T: Compare drawings by data representation dataRepresentation() is for persistence and interchange, not comparison. Use PKDrawing equality for exact value checks, and inspect strokes or rendered images for visual/approximate comparisons. Review Checklist [ ] PKCanvasView.drawingPolicy follows the canonical policy table [ ] PKToolPicker stored as a property, not recreated each appearance [ ] canvasView.becomeFirstResponder() called to show the tool picker [ ] Canvas added as a PKToolPicker observer before showing the picker [ ] Drawing serialized via dataRepresentation() and loaded via PKDrawing(data:) [ ] canvasViewDrawingDidChange delegate method used to track changes [ ] maximumSupportedContentVersion set on both canvas and tool picker if backward compatibility is needed [ ] Custom tool picker item code guarded for iOS/iPadOS 18+ and visionOS 2+ [ ] Exported images use appropriate scale factor for the device [ ] SwiftUI wrapper avoids infinite update loops by checking drawing != binding [ ] Drawing bounds checked before image export (empty drawings have .zero bounds) References Extended PencilKit patterns (advanced strokes, content versions, delegates): [references/pencilkit patterns.md](references/pencilkit patterns.md) [PencilKit framework](https://sosumi.ai/documentation/pencilkit) [PKCanvasView](https://sosumi.ai/documentation/pencilkit/pkcanvasview) [PKDrawing](https://sosumi.ai/documentation/pencilkit/pkdrawing swift.struct) [PKToolPicker](https://sosumi.ai/documentation/pencilkit/pktoolpicker) [PKInkingTool](https://sosumi.ai/documentation/pencilkit/pkinkingtool swift.struct) [PKStroke](https://sosumi.ai/documentation/pencilkit/pkstroke swift.struct) [Drawing with PencilKit](https://sosumi.ai/documentation/pencilkit/drawing with pencilkit) [Configuring the PencilKit tool picker](https://sosumi.ai/documentation/pencilkit/configuring the pencilkit tool picker)