Scale Shapes From An Actual Size Instead Of 0 SwiftUI

Question

I am trying to make pulse animation for an app I am making using swiftui. I want a center gray circle to pulse. Currently, the outside circles scale from 0 but I would like them to start from the middle circle size. This is my current code:

import SwiftUI

struct Pulse: View {
    
    @State var animate = false
    @State private var scale: CGFloat = 2
    var body: some View {
        ZStack
        {
            Circle()
                .fill(Color.black)
                .frame(width: 130, height: 130)
            Circle()
                .stroke(Color.red.opacity(0.1), lineWidth: 5)
                .frame(width: 300, height: 300)
                .scaleEffect(self.animate ? 1 : 0)
            Circle()
                .stroke(Color.red.opacity(0.15), lineWidth: 5)
                .frame(width: 266, height: 266)
                .scaleEffect(self.animate ? 1 : 0)
            
            Circle()
                .stroke(Color.red.opacity(0.2), lineWidth: 5)
                .frame(width: 232, height: 232)
                .scaleEffect(self.animate ? 1 : 0)
            
            Circle()
                .stroke(Color.red.opacity(0.3), lineWidth: 5)
                .frame(width: 198, height: 198)
                .scaleEffect(self.animate ? 1 : 0)
            
            Circle()
                .stroke(Color.red.opacity(0.35), lineWidth: 5)
                .frame(width: 164, height: 164)
                .scaleEffect(self.animate ? 1 : 0)
            
            Circle()
                .stroke(Color.red.opacity(0.4), lineWidth: 5)
                .frame(width: 130, height: 130)
                .scaleEffect(self.animate ? 1 : 0)

            
            Circle()
                .fill(Color.gray)
                .frame(width: 130, height: 130)
            
        }
        .frame(width: 290, height: 290, alignment: .center)
        .onAppear(perform: {
            self.animate.toggle()
        })
        .animation(Animation.linear(duration: 6).repeatForever(autoreverses: true))
        .ignoresSafeArea()
    }
}

Answer 1

The ratio of the size of the inner circle to the outer circle is 130 / 300. At its smallest, you want the circle with width and height of 300 to be 130.

Change all of these:

.scaleEffect(self.animate ? 1 : 0)

to:

.scaleEffect(self.animate ? 1 : 130 / 300)