ViewModifier for resizing images in SwiftUI. Resize an image to any size (square, circle, rectangle) while maintaining its aspect ratio.

swiftui-resize-image-and-maintain-aspect-ratio.swift

import SwiftUI

/// Common aspect ratios
public enum AspectRatio: CGFloat {
    case square = 1
    case threeToFour = 0.75
    case fourToThree = 1.75
}

/// Fit an image to a certain aspect ratio while maintaining its aspect ratio
public struct FitToAspectRatio: ViewModifier {
    
    private let aspectRatio: CGFloat
    
    public init(_ aspectRatio: CGFloat) {
        self.aspectRatio = aspectRatio
    }
    
    public init(_ aspectRatio: AspectRatio) {
        self.aspectRatio = aspectRatio.rawValue
    }
    
    public func body(content: Content) -> some View {
        ZStack {
            Rectangle()
                .fill(Color(.clear))
                .aspectRatio(aspectRatio, contentMode: .fit)

            content
                .scaledToFill()
                .layoutPriority(-1)
        }
        .clipped()
    }
}

// Image extension that composes with the `.resizable()` modifier
public extension Image {
    func fitToAspectRatio(_ aspectRatio: CGFloat) -> some View {
        self.resizable().modifier(FitToAspectRatio(aspectRatio))
    }
    
    func fitToAspectRatio(_ aspectRatio: AspectRatio) -> some View {
        self.resizable().modifier(FitToAspectRatio(aspectRatio))
    }
}