How to stroke on UIImage?

Question

I would like to save the colored shapes along with strokes but the code below (getImage()) generates unstroked shapes:

func getImage() -> UIImage {
        let renderer = UIGraphicsImageRenderer(size: CGSize(width: 1024, height: 1024))
        let image = renderer.image { (context) in
            for key in shapeItemKeys {
                let currentShape = shapeItemsByKey[key]!
                UIColor.black.setStroke()
                context.stroke(renderer.format.bounds)
                currentShape.color.setFill()
                context.cgContext.addPath(currentShape.path.bezierPath.cgPath)
                context.cgContext.fillPath()
                context.cgContext.strokePath()
            }
        }
        return image
    }

struct ShapeItem: Identifiable {
    let id = UUID()
    var color: UIColor = UIColor.white
    var path: ScaledBezier
    init(path: ScaledBezier) {
        self.path = path
    }
}

struct ScaledBezier: Shape {
    let bezierPath: UIBezierPath
    let sourceWidth: CGFloat
    let sourceHeight: CGFloat
    
    func path(in rect: CGRect) -> Path {
        var path = Path(bezierPath.cgPath)
        
        // Figure out how much bigger we need to make our path in order for it to fill the available space without clipping.
        let multiplier = min(rect.width/sourceWidth, rect.height/sourceHeight)
        
        // Create an affine transform that uses the multiplier for both dimensions equally.
        let transform = CGAffineTransform(scaleX: multiplier, y: multiplier)
        
        // Apply that scale and send back the result.
        path.closeSubpath()
        return path.applying(transform)
    }
}

Does anyone know how to stroke shapes in order to be visible on UIImage?

Answer 1

If you want and to stroke and to fill then you need to use path for each as follows

func getImage() -> UIImage {
        let renderer = UIGraphicsImageRenderer(size: CGSize(width: 1024, height: 1024))
        let image = renderer.image { (context) in
            for key in shapeItemKeys {
                let currentShape = shapeItemsByKey[key]!
                UIColor.black.setStroke()
                context.stroke(renderer.format.bounds)
                currentShape.color.setFill()
                context.cgContext.addPath(currentShape.path.bezierPath.cgPath)
                context.cgContext.strokePath()
                context.cgContext.addPath(currentShape.path.bezierPath.cgPath)
                context.cgContext.fillPath()
            }
        }
        return image
    }

Demo code:

struct DemoView: View {

    let shapeItemKeys = [1]
    let shapeItemsByKey = [1: ShapeItem(path: ScaledBezier(bezierPath: UIBezierPath(roundedRect: CGRect(x: 10, y: 10, width: 100, height: 200), cornerRadius: 20), sourceWidth: 100, sourceHeight: 200))]

    var body: some View {
        VStack(spacing: 0) {
            Image(uiImage: getImage())
        }
    }
    func getImage() -> UIImage {
            let renderer = UIGraphicsImageRenderer(size: CGSize(width: 300, height: 300))
            let image = renderer.image { (context) in
                for key in shapeItemKeys {
                    let currentShape = shapeItemsByKey[key]!
                    UIColor.black.setStroke()
                    context.stroke(renderer.format.bounds)
                    currentShape.color.setFill()
                    context.cgContext.addPath(currentShape.path.bezierPath.cgPath)
                    context.cgContext.strokePath()
                    context.cgContext.addPath(currentShape.path.bezierPath.cgPath)
                    context.cgContext.fillPath()
                }
            }
            return image
        }
}