A demo of applying CIFilters to Swift Images, trying to apply a glow effect

Image+Outline-CIFilter.swift

import SwiftUI
import UIKit
import CoreImage
import PlaygroundSupport


extension CIImage {
    convenience init(_ uiImage: UIImage) {
        if let cgImage = uiImage.cgImage {
            self.init(cgImage: cgImage)
        } else {
            self.init()
        }
    }
    
    func bloom(intensity: Float = 1.0, radius: Float = 2) -> CIImage {
        let ctx = CIContext()
        guard let filter = CIFilter(name: "CIBloom") else { fatalError("Filter Unavailable") }
        filter.setValue(self, forKey: kCIInputImageKey)
        filter.setValue(intensity, forKey: kCIInputIntensityKey)
        filter.setValue(radius, forKey: kCIInputRadiusKey)
        return  filter.outputImage ?? CIImage.empty()
    }
    
    func edges(intensity: Float = 1.0) -> CIImage {
        let ctx = CIContext()
        guard let filter = CIFilter(name: "CIEdges") else { fatalError("Filter Unavailable") }
        filter.setValue(self, forKey: kCIInputImageKey)
        filter.setValue(intensity, forKey: kCIInputIntensityKey)
        return  filter.outputImage ?? CIImage.empty()
    }
}


extension Image {
    init(_ cgImage: CGImage) {
        self.init(cgImage, scale: 1.0, orientation: .up, label: Text(""))
    }
    init(_ uiImage: UIImage) {
        guard let cgImage = uiImage.cgImage else { fatalError("Nil CGImage for UIImage") }
        self.init(cgImage)
    }
    init(_ ciImage: CIImage) {
        let context = CIContext(options: nil)
        if let cgImage = context.createCGImage(ciImage, from: ciImage.extent) {
            self.init(cgImage, scale: 1.0, orientation: .up, label: Text(""))
        } else {
            self.init(systemName: "unknown")
        }
    }
}

struct BorderedSymbol: View {
    let symbolName: String
    let symbolColor: Color
    let borderColor: Color

    var body: some View {
        let image = UIImage(systemName: symbolName)!
        let edged = CIImage(image).edges().bloom()
        ZStack {
            Image(edged)
                .renderingMode(.template)
                .foregroundColor(borderColor)
            Image(image)
                .renderingMode(.template)
                .foregroundColor(symbolColor)
        }
    }
}

let bordered = BorderedSymbol(symbolName: "pin.circle", symbolColor: .orange, borderColor: .blue)
    .imageScale(.large)
    .scaleEffect(1.0)
    .frame(width: 100, height: 100)

PlaygroundPage.current.setLiveView(bordered)

Some nice references that helped:

• https://github.com/danwood/SwiftUICoreImage
• Apple Doc on Processing Images with CIFilters
• Apple's Core Image Filter Reference