iOS SwiftUI 颜色渐变填充效果的实现

SwiftUI 为我们提供了各种梯度选项，所有这些选项都可以通过多种方式使用。

Gradient 渐变器

A color gradient represented as an array of color stops, each having a parametric location value.

gradient是一组颜色的合集，每个颜色都忽略位置参数

LinearGradient 线性渐变器

线性渐变器拥有沿轴进行渐变函数，我们可以自定义设置颜色空间、起点和终点。

下面我们看看LinearGradient效果

import SwiftUI

struct LineView: View {
   var gradient: Gradient {
      let stops: [Gradient.Stop] = [
        .init(color: .red, location: 0.5),
        .init(color: .yellow, location: 0.5)
      ]
      return Gradient(stops: stops)
    }
    
    var body: some View {
    
        ZStack {
          LinearGradient(gradient: gradient,
                 startPoint: .top,
                 endPoint: .trailing)
            .edgesIgnoringSafeArea(.all)
          
          Image("1")
            .resizable()
            .aspectRatio(contentMode: .fit)
            .clipShape(Circle())
            .overlay(Circle()
              .stroke(lineWidth: 8)
              .foregroundColor(.white))
            .frame(width: 250)
          
        Text("洛神赋图")
              .padding()
              .foregroundColor(.white)
          .cornerRadius(8)
              .background(LinearGradient(gradient: Gradient(colors: [.white, .black]), startPoint: .top, endPoint: .bottom))
          .offset(y:-280)
        }

    }
}

import SwiftUI

struct LineGradient3Color: View {
  
  var body: some View {
    ZStack {
      LinearGradient(gradient:
        Gradient(
          colors: [.blue, .white, .pink]),
              startPoint: .topLeading,
              endPoint: .bottomTrailing)
        .edgesIgnoringSafeArea(.all)
      
      Image("2")
        .resizable()
        .aspectRatio(contentMode: .fit)
        .clipShape(Circle())
        .overlay(Circle()
          .stroke(lineWidth: 8)
          .foregroundColor(.white))
        .frame(width: 250)
      
      Text("清明上河图")
        .padding()
        .foregroundColor(.white)
        .cornerRadius(8)
        .background(LinearGradient(gradient: Gradient(
          colors: [.yellow, .red]),
                      startPoint: .topLeading,
          endPoint: .bottomTrailing))
        .offset(y:-180)
    }
  }
}

Radial Gradient 径向渐变

在径向渐变中，我们必须指定起始半径点，端半径点与中心点，从径向渐变开变.

import SwiftUI

struct RadialView: View {
   var body: some View {
     ZStack {
       RadialGradient(gradient: Gradient(
        colors: [.blue, .black]),
        center: .center,
        startRadius: 2,
        endRadius: 650)
         .edgesIgnoringSafeArea(.all)
       
       Image("3")
         .resizable()
         .aspectRatio(contentMode: .fit)
         .clipShape(Circle())
         .overlay(Circle()
           .stroke(lineWidth: 8)
           .foregroundColor(.white))
         .frame(width: 250)
       
       Text("富春山居图")
         .padding()
         .foregroundColor(.white)
         .cornerRadius(8)
         .background(
          RadialGradient(gradient: Gradient(
           colors: [.yellow, .red]),
                  center: .center,
                   startRadius: 2,
               endRadius: 60))
         .offset(y:-180)
     }
   }
}

Angular Gradient

在角渐变中，我们只需要通过中心点。

import SwiftUI

struct AngularView: View {
    var body: some View {
     ZStack {
      AngularGradient(gradient: Gradient(
        colors: [.green, .blue, .black, .green, .blue, .black, .green]),
        center: .center)
         .edgesIgnoringSafeArea(.all)
       
       Image("4")
         .resizable()
         .aspectRatio(contentMode: .fit)
         .clipShape(Circle())
         .overlay(Circle()
           .stroke(lineWidth: 8)
           .foregroundColor(.white))
         .frame(width: 250)
       
       Text("汉宫春晓图")
         .padding()
         .foregroundColor(.white)
         .cornerRadius(8)
         .background(
          RadialGradient(gradient: Gradient(
           colors: [.yellow, .red]),
                 center: .center,
                   startRadius: 2,
              endRadius: 60))
         .offset(y:-180)
     }
   }

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