JJBB/Assets/Project/Script/GUI/Base/ScratchTicket.cs

using System;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
using UnityEngine.Events;

[RequireComponent(typeof(RawImage))]
public class ScratchTicket : MonoBehaviour
{
    public Camera uiCamera
    {
        get { return UIManager.Instance().UICamera; }
    }

    /// <summary>
    /// 笔刷半径，单位为Ui长度
    /// </summary>
    public float radius = 20f;

    /// <summary>
    /// RenderTexture尺寸比例
    /// </summary>
    public float renderTexRadio = 0.5f;

    public event UnityAction<float> onCleanRatioUpdate;

    /// <summary>
    /// 当前清空程度
    /// </summary>
    private float _cleanPixel;

    public float cleanRatio
    {
        get
        {
            if (_renderTexture == null)
                return 0f;
            else
            {
                var pixelCount = _renderTexture.width * _renderTexture.height;
                return pixelCount > 0 ? _cleanPixel / pixelCount : 1f;
            }
        }
    }

    private RawImage _rawImage;
    private Texture2D _renderTexture;
    private Material _renderMaterial;

    private Vector2 _min;
    private Vector2 _max;
    private bool _start;

    private void Awake()
    {
        _rawImage = GetComponent<RawImage>();
        var rect = _rawImage.rectTransform.rect;
        _min = rect.min;
        _max = rect.max;
        var dragComponent = gameObject.EnsureComponent<UiDragComponent>();
        dragComponent.onDrag += OnDrag;
    }

    private void OnEnable()
    {
        if (_start)
            Reset();
    }

    private void Start()
    {
        if (renderTexRadio <= 0f)
            renderTexRadio = 1f;
        if (_renderTexture == null)
        {
            var width = Mathf.FloorToInt((_max.x - _min.x) * renderTexRadio);
            var height = Mathf.FloorToInt((_max.y - _min.y) * renderTexRadio);
            _renderTexture = new Texture2D(width, height, TextureFormat.ARGB32, false);
        }

        _renderMaterial = _rawImage.material;
        if (_renderMaterial != null)
        {
            _renderMaterial = Instantiate(_renderMaterial);
            _rawImage.material = _renderMaterial;
            _renderMaterial.SetTexture("_ScratchTex", _renderTexture);
        }

        _start = true;
        OnEnable();
    }

    private void OnDestroy()
    {
        if (_renderMaterial != null)
            Destroy(_renderMaterial);
        if (_renderTexture != null)
            Destroy(_renderTexture);
    }

    public void OnDrag(Vector2 lastPoint, Vector2 currentPoint)
    {
        var pixelRadius = radius / (_max.x - _min.x) * _renderTexture.width;
        if (pixelRadius > 0)
        {
            Vector2 start;
            Vector2 end;
            if (RectTransformUtility.ScreenPointToLocalPointInRectangle(_rawImage.rectTransform, lastPoint, uiCamera,
                    out start) &&
                RectTransformUtility.ScreenPointToLocalPointInRectangle(_rawImage.rectTransform, currentPoint, uiCamera,
                    out end))
            {
                var radiusSqr = pixelRadius * pixelRadius;
                var width = _renderTexture.width;
                var height = _renderTexture.height;
                start = LocalPointToPixelPos(start);
                end = LocalPointToPixelPos(end);
                var dirty = false;
                for (var x = 0; x < width; x++)
                {
                    for (var y = 0; y < height; y++)
                    {
                        var distSqr = DistanceSqrToLine(new Vector2(x, y), start, end);
                        if (distSqr < radiusSqr)
                        {
                            var ratio = distSqr / radiusSqr;
                            if (ratio < 0.1f)
                                ratio = 0f;
                            var color = _renderTexture.GetPixel(x, y);
                            if (color.a > ratio)
                            {
                                dirty = true;
                                _cleanPixel += color.a - ratio;
                                color.a = ratio;
                                _renderTexture.SetPixel(x, y, color);
                            }
                        }
                    }
                }

                if (dirty)
                {
                    _renderTexture.Apply();
                    if (onCleanRatioUpdate != null)
                        onCleanRatioUpdate.Invoke(cleanRatio);
                }

            }
        }
    }

    private Vector2 LocalPointToPixelPos(Vector2 localPoint)
    {
        var uv = new Vector2(
            (localPoint.x - _min.x) / (_max.x - _min.x),
            (localPoint.y - _min.y) / (_max.y - _min.y));
        uv.x = uv.x * _renderTexture.width;
        uv.y = uv.y * _renderTexture.height;
        return uv;
    }
    
    private float DistanceSqrToLine(Vector2 point, Vector2 start, Vector2 end)
    {
        var a = DistanceSqrToPoint(point, start);
        if (a < 0.0001f)
            return 0f;
        var b = DistanceSqrToPoint(point, end);
        if (b < 0.0001f)
            return 0f;
        var c = DistanceSqrToPoint(start, end);
        if (c < 0.0001f)
            return a;
        if (a > b + c)
            return b;
        if (b > a + c)
            return a;
        var la = Mathf.Sqrt(a);
        var lb = Mathf.Sqrt(b);
        var lc = Mathf.Sqrt(c);
        var l = (la + lb + lc) * 0.5f;
        l = l * (l - la) * (l - lb) * (l - lc);
        return 4 * l / c;
    }

    private float DistanceSqrToPoint(Vector2 point, Vector2 end)
    {
        return (point.x - end.x) * (point.x - end.x) + (point.y - end.y) * (point.y - end.y);
    }

    public void Reset()
    {
        _cleanPixel = 0f;
        if (_renderTexture != null)
        {
            var colors = _renderTexture.GetPixels();
            for (var i = 0; i < colors.Length; i++)
            {
                var color = colors[i];
                color.a = 1f;
                colors[i] = color;
            }

            _renderTexture.SetPixels(colors);
            _renderTexture.Apply();
        }
    }
}