Learn the geometry, drawing state, and image representations behind custom rendering on iOS. The topics progress from a drawing context to reusable renderers and performance checks. Article links will be added to this outline as content becomes available.
Article available Coming soon
1. Geometry and Contexts
- Points, Sizes, Rectangles, and Coordinate Systems
- Points vs. Pixels and Display Scale
- Drawing with
CGContext - Saving and Restoring Graphics State
- Translation, Rotation, and Affine Transforms
2. Paths and Appearance
- Building Paths with Lines and Bézier Curves
- Filling and Stroking Paths
- Line Width, Joins, Caps, and Dash Patterns
- Clipping Regions and Image Masks
- Gradients, Blend Modes, and Compositing
3. Images and Documents
CGImage,UIImage, and Image Orientation- Bitmap Contexts, Pixel Formats, and Color Spaces
- Resizing, Cropping, and Drawing Images
- Rendering Scalable Content into PDF
- Exporting Images with the Right Scale and Format
4. Rendering in an App
- Custom View Drawing and Invalidation
- Reusable Drawing Functions with Explicit Inputs
- Separating Geometry from UIKit and SwiftUI Rendering
- Rendering Offscreen Without Sharing Unsafe State
- Caching Rendered Output and Invalidating It Correctly
5. Verification and Performance
- Testing Geometry and Hit Regions
- Snapshot Testing with Controlled Rendering Inputs
- Reducing Overdraw and Repeated Drawing Work
- Profiling Image Memory and Rendering Cost
Up next
Core Animation