// ============================================================================
// Copyright © 2026 Hexagon Technology Center GmbH. All Rights Reserved.
// 文件名: RetinexProcessor.cs
// 描述: 基于Retinex的多尺度阴影校正算子（支持 8 位 / 16 位）
// 功能:
//   - 单尺度Retinex (SSR)
//   - 多尺度Retinex (MSR)
//   - 带色彩恢复的多尺度Retinex (MSRCR)
//   - 光照不均匀校正
//   - 阴影去除
// 算法: Retinex理论 - 将图像分解为反射分量和光照分量
// 作者: 李伟 wei.lw.li@hexagon.com
// ============================================================================

using Emgu.CV;
using Emgu.CV.Structure;
using XP.ImageProcessing.Core;
using Serilog;

namespace XP.ImageProcessing.Processors;

/// <summary>
/// Retinex多尺度阴影校正算子（支持 8 位和 16 位灰度图像）。
/// 全程在浮点对数域运算，输入按位深转 float、输出经 min-max 归一化回目标位深，无 8 位降位损失。
/// </summary>
public class RetinexProcessor<TDepth> : ImageProcessorBase<TDepth>
    where TDepth : struct, IComparable
{
    private static readonly ILogger _logger = Log.ForContext<RetinexProcessor<TDepth>>();

    public RetinexProcessor()
    {
        Name = LocalizationHelper.GetString("RetinexProcessor_Name");
        Description = LocalizationHelper.GetString("RetinexProcessor_Description");
    }

    protected override void InitializeParameters()
    {
        Parameters.Add("Method", new ProcessorParameter(
            "Method",
            LocalizationHelper.GetString("RetinexProcessor_Method"),
            typeof(string),
            "MSR",
            null,
            null,
            LocalizationHelper.GetString("RetinexProcessor_Method_Desc"),
            new string[] { "SSR", "MSR", "MSRCR" }) { IsAdvanced = true });

        Parameters.Add("Sigma1", new ProcessorParameter(
            "Sigma1",
            LocalizationHelper.GetString("RetinexProcessor_Sigma1"),
            typeof(double),
            15.0,
            1.0,
            100.0,
            LocalizationHelper.GetString("RetinexProcessor_Sigma1_Desc")) { IsAdvanced = true });

        Parameters.Add("Sigma2", new ProcessorParameter(
            "Sigma2",
            LocalizationHelper.GetString("RetinexProcessor_Sigma2"),
            typeof(double),
            80.0,
            1.0,
            200.0,
            LocalizationHelper.GetString("RetinexProcessor_Sigma2_Desc")) { IsAdvanced = true });

        Parameters.Add("Sigma3", new ProcessorParameter(
            "Sigma3",
            LocalizationHelper.GetString("RetinexProcessor_Sigma3"),
            typeof(double),
            250.0,
            1.0,
            500.0,
            LocalizationHelper.GetString("RetinexProcessor_Sigma3_Desc")) { IsAdvanced = true });

        Parameters.Add("Gain", new ProcessorParameter(
            "Gain",
            LocalizationHelper.GetString("RetinexProcessor_Gain"),
            typeof(double),
            1.0,
            0.1,
            5.0,
            LocalizationHelper.GetString("RetinexProcessor_Gain_Desc")));

        Parameters.Add("Offset", new ProcessorParameter(
            "Offset",
            LocalizationHelper.GetString("RetinexProcessor_Offset"),
            typeof(int),
            0,
            -100,
            100,
            LocalizationHelper.GetString("RetinexProcessor_Offset_Desc")) { IsAdvanced = true });
        _logger.Debug("InitializeParameters");
    }

    public override Image<Gray, TDepth> Process(Image<Gray, TDepth> inputImage)
    {
        string method = GetParameter<string>("Method");
        double sigma1 = GetParameter<double>("Sigma1");
        double sigma2 = GetParameter<double>("Sigma2");
        double sigma3 = GetParameter<double>("Sigma3");
        double gain = GetParameter<double>("Gain");
        int offset = GetParameter<int>("Offset");

        // Offset 参数按 8 位语义定义（对数域偏移），16 位无需放大（对数域偏移与位深无关，
        // 但为保持与 8 位一致的视觉效果，此处不缩放，仅作用于对数域）
        Image<Gray, TDepth> result;

        if (method == "SSR")
        {
            result = SingleScaleRetinex(inputImage, sigma2, gain, offset);
        }
        else if (method == "MSR")
        {
            result = MultiScaleRetinex(inputImage, new[] { sigma1, sigma2, sigma3 }, gain, offset);
        }
        else // MSRCR
        {
            result = MultiScaleRetinexCR(inputImage, new[] { sigma1, sigma2, sigma3 }, gain, offset);
        }

        _logger.Debug("Process: Method = {Method}, Sigma1 = {Sigma1}, Sigma2 = {Sigma2}, Sigma3 = {Sigma3}, Gain = {Gain}, Offset = {Offset}",
            method, sigma1, sigma2, sigma3, gain, offset);
        return result;
    }

    /// <summary>
    /// 单尺度Retinex (SSR)
    /// R(x,y) = log(I(x,y)) - log(I(x,y) * G(x,y))
    /// </summary>
    private Image<Gray, TDepth> SingleScaleRetinex(Image<Gray, TDepth> inputImage, double sigma, double gain, int offset)
    {
        int w = inputImage.Width, h = inputImage.Height;

        // 转换为浮点图像并添加小常数避免log(0)
        Image<Gray, float> floatImage = inputImage.Convert<Gray, float>();
        floatImage = floatImage + 1.0f;

        // 计算log(I)
        var logImage = new Image<Gray, float>(w, h);
        for (int y = 0; y < h; y++)
            for (int x = 0; x < w; x++)
                logImage.Data[y, x, 0] = (float)Math.Log(floatImage.Data[y, x, 0]);

        // 高斯模糊得到光照分量
        var blurred = new Image<Gray, float>(w, h);
        int kernelSize = (int)(sigma * 6) | 1;
        if (kernelSize < 3) kernelSize = 3;
        CvInvoke.GaussianBlur(floatImage, blurred, new System.Drawing.Size(kernelSize, kernelSize), sigma);

        // 计算log(I * G)
        var logBlurred = new Image<Gray, float>(w, h);
        for (int y = 0; y < h; y++)
            for (int x = 0; x < w; x++)
                logBlurred.Data[y, x, 0] = (float)Math.Log(blurred.Data[y, x, 0]);

        // R = log(I) - log(I*G)
        var retinex = logImage - logBlurred;

        // 应用增益和偏移
        retinex = retinex * gain + offset;

        var result = PixelDepthHelper.FromFloatImage<TDepth>(retinex);

        floatImage.Dispose();
        logImage.Dispose();
        blurred.Dispose();
        logBlurred.Dispose();
        retinex.Dispose();

        return result;
    }

    /// <summary>
    /// 多尺度Retinex (MSR)
    /// MSR = Σ(w_i * SSR_i) / N
    /// </summary>
    private Image<Gray, TDepth> MultiScaleRetinex(Image<Gray, TDepth> inputImage, double[] sigmas, double gain, int offset)
    {
        int w = inputImage.Width, h = inputImage.Height;

        Image<Gray, float> floatImage = inputImage.Convert<Gray, float>();
        floatImage = floatImage + 1.0f;

        var logImage = new Image<Gray, float>(w, h);
        for (int y = 0; y < h; y++)
            for (int x = 0; x < w; x++)
                logImage.Data[y, x, 0] = (float)Math.Log(floatImage.Data[y, x, 0]);

        var msrResult = new Image<Gray, float>(w, h);
        msrResult.SetZero();

        foreach (double sigma in sigmas)
        {
            var blurred = new Image<Gray, float>(w, h);
            int kernelSize = (int)(sigma * 6) | 1;
            if (kernelSize < 3) kernelSize = 3;
            CvInvoke.GaussianBlur(floatImage, blurred, new System.Drawing.Size(kernelSize, kernelSize), sigma);

            var logBlurred = new Image<Gray, float>(w, h);
            for (int y = 0; y < h; y++)
                for (int x = 0; x < w; x++)
                    logBlurred.Data[y, x, 0] = (float)Math.Log(blurred.Data[y, x, 0]);

            msrResult = msrResult + (logImage - logBlurred);

            blurred.Dispose();
            logBlurred.Dispose();
        }

        msrResult = msrResult / sigmas.Length;
        msrResult = msrResult * gain + offset;

        var result = PixelDepthHelper.FromFloatImage<TDepth>(msrResult);

        floatImage.Dispose();
        logImage.Dispose();
        msrResult.Dispose();

        return result;
    }

    /// <summary>
    /// 带色彩恢复的多尺度Retinex (MSRCR)
    /// 对于灰度图像，使用简化版本
    /// </summary>
    private Image<Gray, TDepth> MultiScaleRetinexCR(Image<Gray, TDepth> inputImage, double[] sigmas, double gain, int offset)
    {
        int w = inputImage.Width, h = inputImage.Height;
        double maxVal = MaxPixelValue;

        // 先执行MSR（得到目标位深结果），再转 float 做色彩恢复
        var msrResult = MultiScaleRetinex(inputImage, sigmas, gain, offset);

        var floatMsr = msrResult.Convert<Gray, float>();
        var floatInput = inputImage.Convert<Gray, float>();

        // 色彩恢复因子：基于原始灰度对数（归一化到位深中点）
        double logMid = Math.Log(maxVal / 2.0 + 1.0);
        var enhanced = new Image<Gray, float>(w, h);
        for (int y = 0; y < h; y++)
            for (int x = 0; x < w; x++)
            {
                float msr = floatMsr.Data[y, x, 0];
                float original = floatInput.Data[y, x, 0];
                float c = (float)(Math.Log(original + 1.0) / logMid);
                enhanced.Data[y, x, 0] = msr * c;
            }

        var result = PixelDepthHelper.FromFloatImage<TDepth>(enhanced);

        msrResult.Dispose();
        floatMsr.Dispose();
        floatInput.Dispose();
        enhanced.Dispose();

        return result;
    }
}