powerfun-unity/Assets/Scenes/Ride/Scripts/GradientBackGround.cs

using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

namespace Assets.Scenes.Ride.Scripts
{
    [RequireComponent(typeof(Image))]
    public class GradientBackGround : MonoBehaviour
    {
        public enum GradientType
        {
            None,
            Vertical,
            VerticalDown,
            Horizontal,
            Diagonal
        }

        [System.Serializable]
        public class GradientColorNode
        {
            [Range(0, 1)]
            public float ratio = 0;
            public Color color = Color.white;

            public GradientColorNode(float _ratio, Color _color)
            {
                ratio = _ratio;
                color = _color;
            }
        }

        private Image bgImage;

        [SerializeField, Header("渐变方式")]
        private GradientType gradientType = GradientType.Vertical;

        [SerializeField, Header("渐变曲线(0~1)")]
        private AnimationCurve gradientCurve = new AnimationCurve(new Keyframe(0, 0), new Keyframe(1, 1));

        [SerializeField, Header("渐变颜色")]
        private List<GradientColorNode> gradientColorNodeList = new List<GradientColorNode>() { new GradientColorNode(0, Color.white), new GradientColorNode(1, Color.black) };

        private void Awake()
        {
            bgImage = GetComponent<Image>();
        }

        private void Start()
        {
            SetGradientColor();
        }

        private void Update()
        {
            //if (Input.GetKeyDown(KeyCode.Alpha1))
            //{
            //    gradientType = GradientType.None;
            //    SetGradientColor();
            //}
            //if (Input.GetKeyDown(KeyCode.Alpha2))
            //{
            //    gradientType = GradientType.Vertical;
            //    SetGradientColor();
            //}
            //if (Input.GetKeyDown(KeyCode.Alpha3))
            //{
            //    gradientType = GradientType.Horizontal;
            //    SetGradientColor();
            //}
            //if (Input.GetKeyDown(KeyCode.Alpha4))
            //{
            //    gradientType = GradientType.Diagonal;
            //    SetGradientColor();
            //}
        }

        private void SetGradientColor()
        {
            //创建Texture2D
            Vector2Int imageSize = new Vector2Int(Screen.width, Screen.height);
            Texture2D texture2D = new Texture2D(imageSize.x, imageSize.y);
            //遍历像素点
            switch (gradientType)
            {
                case GradientType.Vertical:
                    for (int y = 0; y < imageSize.y; y++)
                    {
                        Color pixelColor = GetColorByCurve(1.0f * y / imageSize.y);
                        for (int x = 0; x < imageSize.x; x++)
                        {
                            texture2D.SetPixel(x, y, pixelColor);
                        }
                    }
                    break;
                case GradientType.VerticalDown:
                    for (int y = imageSize.y - 1; y > 0; y--)
                    {
                        Color pixelColor = GetColorByCurve(1.0f * y / imageSize.y);
                        for (int x = imageSize.x - 1; x > 0; x--)
                        {
                            texture2D.SetPixel(x, y, pixelColor);
                        }
                    }
                    break;
                case GradientType.Horizontal:
                    for (int x = 0; x < imageSize.x; x++)
                    {
                        Color pixelColor = GetColorByCurve(1.0f * x / imageSize.x);
                        for (int y = 0; y < imageSize.y; y++)
                        {
                            texture2D.SetPixel(x, y, pixelColor);
                        }
                    }
                    break;
                case GradientType.Diagonal:
                    for (int x = 0; x < imageSize.x; x++)
                    {
                        for (int y = 0; y < imageSize.y; y++)
                        {
                            Color pixelColor = GetColorByCurve(0.5f * x / imageSize.x + 0.5f * y / imageSize.y);
                            texture2D.SetPixel(x, y, pixelColor);
                        }
                    }
                    break;
                default:
                    if (gradientColorNodeList.Count > 0)
                    {
                        Color pixelColor = gradientColorNodeList[0].color;
                        for (int x = 0; x < imageSize.x; x++)
                        {
                            for (int y = 0; y < imageSize.y; y++)
                            {
                                texture2D.SetPixel(x, y, pixelColor);
                            }
                        }
                    }
                    break;
            }
            texture2D.Apply();
            //创建Sprite
            Sprite sprite = Sprite.Create(texture2D, new Rect(0, 0, imageSize.x, imageSize.y), new Vector2(0.5f, 0.5f));
            sprite.name = "GradientBg";
            if (bgImage != null)
                bgImage.sprite = sprite;
        }

        private Color GetColorByCurve(float ratio)
        {
            for (int i = 1; i < gradientColorNodeList.Count; i++)
            {
                if (ratio < gradientColorNodeList[i].ratio)
                {
                    float curveValue = (ratio - gradientColorNodeList[i - 1].ratio) / (gradientColorNodeList[i].ratio - gradientColorNodeList[i - 1].ratio);
                    curveValue = gradientCurve.Evaluate(curveValue);
                    return Color.Lerp(gradientColorNodeList[i - 1].color, gradientColorNodeList[i].color, curveValue);
                }
            }
            return Color.white;
        }

    }
}