Utilise the private CoreSVG framework in Swift

SVG.swift

import Darwin
import Foundation
import UIKit

// https://github.com/xybp888/iOS-SDKs/blob/master/iPhoneOS17.1.sdk/System/Library/PrivateFrameworks/CoreSVG.framework/CoreSVG.tbd
// https://developer.limneos.net/index.php?ios=17.1&framework=UIKitCore.framework&header=UIImage.h

@objc
class CGSVGDocument: NSObject { }

var CGSVGDocumentRetain: (@convention(c) (CGSVGDocument?) -> Unmanaged<CGSVGDocument>?) = load("CGSVGDocumentRetain")
var CGSVGDocumentRelease: (@convention(c) (CGSVGDocument?) -> Void) = load("CGSVGDocumentRelease")
var CGSVGDocumentCreateFromData: (@convention(c) (CFData?, CFDictionary?) -> Unmanaged<CGSVGDocument>?) = load("CGSVGDocumentCreateFromData")
var CGContextDrawSVGDocument: (@convention(c) (CGContext?, CGSVGDocument?) -> Void) = load("CGContextDrawSVGDocument")
var CGSVGDocumentGetCanvasSize: (@convention(c) (CGSVGDocument?) -> CGSize) = load("CGSVGDocumentGetCanvasSize")

typealias ImageWithCGSVGDocument = @convention(c) (AnyObject, Selector, CGSVGDocument) -> UIImage
var ImageWithCGSVGDocumentSEL: Selector = NSSelectorFromString("_imageWithCGSVGDocument:")

let CoreSVG = dlopen("/System/Library/PrivateFrameworks/CoreSVG.framework/CoreSVG", RTLD_NOW)

func load<T>(_ name: String) -> T {
    unsafeBitCast(dlsym(CoreSVG, name), to: T.self)
}

public class SVG {
    
    deinit { CGSVGDocumentRelease(document) }
    
    let document: CGSVGDocument

    public convenience init?(_ value: String) {
        guard let data = value.data(using: .utf8) else { return nil }
        self.init(data)
    }
    
    public init?(_ data: Data) {
        guard let document = CGSVGDocumentCreateFromData(data as CFData, nil)?.takeUnretainedValue() else { return nil }
        guard CGSVGDocumentGetCanvasSize(document) != .zero else { return nil }
        self.document = document
    }
    
    public var size: CGSize {
        CGSVGDocumentGetCanvasSize(document)
    }
    
    public func image() -> UIImage? {
        let ImageWithCGSVGDocument = unsafeBitCast(UIImage.self.method(for: ImageWithCGSVGDocumentSEL), to: ImageWithCGSVGDocument.self)
        let image = ImageWithCGSVGDocument(UIImage.self, ImageWithCGSVGDocumentSEL, document)
        return image
    }
    
    public func draw(in context: CGContext) {
        draw(in: context, size: size)
    }
    
    public func draw(in context: CGContext, size target: CGSize) {

        var target = target
        
        let ratio = (
            x: target.width / size.width,
            y: target.height / size.height
        )
        
        let rect = (
            document: CGRect(origin: .zero, size: size), ()
        )

        let scale: (x: CGFloat, y: CGFloat)
        
        if target.width <= 0 {
            scale = (ratio.y, ratio.y)
            target.width = size.width * scale.x
        } else if target.height <= 0 {
            scale = (ratio.x, ratio.x)
            target.width = size.width * scale.y
        } else {
            let min = min(ratio.x, ratio.y)
            scale = (min, min)
            target.width = size.width * scale.x
            target.height = size.height * scale.y
        }

        let transform = (
            scale: CGAffineTransform(scaleX: scale.x, y: scale.y),
            aspect: CGAffineTransform(translationX: (target.width / scale.x - rect.document.width) / 2, y: (target.height / scale.y - rect.document.height) / 2)
        )
        
        context.translateBy(x: 0, y: target.height)
        context.scaleBy(x: 1, y: -1)
        context.concatenate(transform.scale)
        context.concatenate(transform.aspect)
        
        CGContextDrawSVGDocument(context, document)
    }
}

let data = """
<svg class="heart-loader" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:svg="http://www.w3.org/2000/svg" xmlns="http://www.w3.org/2000/svg"
xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 90 90" version="1.1">
<g class="heart-loader__group">
<path class="heart-loader__square" stroke-width="1" fill="none" d="M0,30 0,90 60,90 60,30z"/>
<path class="heart-loader__circle m--left" stroke-width="1" fill="none" d="M60,60 a30,30 0 0,1 -60,0 a30,30 0 0,1 60,0"/>
<path class="heart-loader__circle m--right" stroke-width="1" fill="none" d="M60,60 a30,30 0 0,1 -60,0 a30,30 0 0,1 60,0"/>
<path class="heart-loader__heartPath" stroke-width="2" d="M60,30 a30,30 0 0,1 0,60 L0,90 0,30 a30,30 0 0,1 60,0" />
</g>
</svg>
""".data(using: .utf8)!

let svg = SVG(data)!

let image = svg.image() // 🖥

let render = UIGraphicsImageRenderer(size: svg.size)
let image2 = render.image { context in
    svg.draw(in: context.cgContext)
} // 🖥

Hi there,
I am trying to use this but I get the following error:

Entity: line 1: parser error : Start tag expected, '<' not found
\211PNG
^
CoreSVG has logged an error. Set environment variabe "CORESVG_VERBOSE" to learn more.
Entity: line 1: parser error : Start tag expected, '<' not found
\211PNG
^

Do you have an idea what this means? I basically just passed Data I got from an URLSession inside of SVGs initializer.

An additional question is it possible to use this to (rasterize) and show SVG images in a SwiftUI Image ? Because that is what I am eventually trying to achieve

Hi there, I am trying to use this but I get the following error:

Entity: line 1: parser error : Start tag expected, '<' not found
\211PNG
^
CoreSVG has logged an error. Set environment variabe "CORESVG_VERBOSE" to learn more.
Entity: line 1: parser error : Start tag expected, '<' not found
\211PNG
^

Do you have an idea what this means? I basically just passed Data I got from an URLSession inside of SVGs initializer.

An additional question is it possible to use this to (rasterize) and show SVG images in a SwiftUI Image ? Because that is what I am eventually trying to achieve

You can try to use UIImage's init(data:) method and then convert it to SwiftUI image like here. UIImage should support SVG natively:

You use image objects to represent image data of all kinds...

yeah, that did not work for vector data though when I tried. Not sure why, but Apple's SVG support seems really limited and therefore a pain.

Loading SVG seems to work only when loading from the bundle.

@misteu When using this in SwiftUI I used UI/NSViewRepresentable and drew the SVG to the graphic context:

struct SVGView: UIViewRepresentable {

    private final class View: UIView {
        var svg: SVG
       init(_ svg: SVG) {
            self.svg = svg
            super.init(frame: .init(origin: .zero, size: svg.size))
            isOpaque = false
        }
        @available(*, unavailable) required init?(coder: NSCoder) { fatalError("init(coder:) has not been implemented") }
        overrid func draw(_ rect: CGRect) {
            guard let context = UIGraphicsGetCurrentContext() else { return }
            svg.draw(in: context, size: rect.size)
        }
    }

    private let svg: SVG
    init(_ svg: SVG) { self.svg = svg }
    
    public func makeUIView(context: Context) -> UIView { 
        View(svg) 
    }
    public func updateUIView(_ view: UIView, context: Context) { 
        view.setNeedsDisplay() 
    }
}

For those wanting to use this inside of production app, I've not been blocked with using this since the initial version in 2021, you just need to obfuscate the symbols

// private var CGSVGDocumentRetain: (@convention(c) (CGSVGDocument?) -> Unmanaged<CGSVGDocument>?) = load("CGSVGDocumentRetain")
private var CGSVGDocumentRetain: (@convention(c) (CGSVGDocument?) -> Unmanaged<CGSVGDocument>?) = load("==gbpFGdlJFduVWb1N2bEdkVTd0Q".deobfuscated)

// private var CGSVGDocumentRelease: (@convention(c) (CGSVGDocument?) -> Void) = load("CGSVGDocumentRelease")
private var CGSVGDocumentRelease: (@convention(c) (CGSVGDocument?) -> Void) = load("=U2chVGblJFduVWb1N2bEdkVTd0Q".deobfuscated)

// private var CGSVGDocumentCreateFromData: (@convention(c) (CFData?, CFDictionary?) -> Unmanaged<CGSVGDocument>?) = load("CGSVGDocumentCreateFromData")
private var CGSVGDocumentCreateFromData: (@convention(c) (CFData?, CFDictionary?) -> Unmanaged<CGSVGDocument>?) = load("hRXYE12byZUZ0FWZyNEduVWb1N2bEdkVTd0Q".deobfuscated)

// private var CGSVGDocumentWriteToData: (@convention(c) (CGSVGDocument?, CFData?, CFDictionary?) -> Void) = load("CGSVGDocumentWriteToData")
private var CGSVGDocumentWriteToData: (@convention(c) (CGSVGDocument?, CFData?, CFDictionary?) -> Void) = load("hRXYE9GVlRXaydFduVWb1N2bEdkVTd0Q".deobfuscated)

// private var CGContextDrawSVGDocument: (@convention(c) (CGContext?, CGSVGDocument?) -> Void) = load("CGContextDrawSVGDocument")
private var CGContextDrawSVGDocument: (@convention(c) (CGContext?, CGSVGDocument?) -> Void) = load("05WZtV3YvR0RWN1dhJHR0hXZ052bDd0Q".deobfuscated)

// private var CGSVGDocumentGetCanvasSize: (@convention(c) (CGSVGDocument?) -> CGSize) = load("CGSVGDocumentGetCanvasSize")
private var CGSVGDocumentGetCanvasSize: (@convention(c) (CGSVGDocument?) -> CGSize) = load("=UmepN1chZnbhNEdldEduVWb1N2bEdkVTd0Q".deobfuscated)

#if canImport(UIKit)
// private typealias ImageWithCGSVGDocument = @convention(c) (AnyObject, Selector, CGSVGDocument) -> UIImage
private typealias ImageWithCGSVGDocument = @convention(c) (AnyObject, Selector, CGSVGDocument) -> UIImage
#endif

// private var ImageWithCGSVGDocumentSEL: Selector = NSSelectorFromString("_imageWithCGSVGDocument:")
private var ImageWithCGSVGDocumentSEL: Selector = NSSelectorFromString("6Qnbl1Wdj9GRHZ1UHNEa0l2VldWYtl2X".deobfuscated)

// private let CoreSVG = dlopen("/System/Library/PrivateFrameworks/CoreSVG.framework/CoreSVG", RTLD_NOW)
private let CoreSVG = dlopen("=ckVTVmcvN0LrJ3b3VWbhJnZuckVTVmcvN0LztmcvdXZtFmcGVGdhZXayB1L5JXYyJWaM9SblR3c5N1L".deobfuscated, RTLD_NOW)

extension String {
    fileprivate var deobfuscated: String { Data(base64Encoded: String(reversed()))!.string }
}

extension Data {
    fileprivate var string: String { String(decoding: self, as: UTF8.self) }
}