// ============================================================================
// Copyright © 2026 Hexagon Technology Center GmbH. All Rights Reserved.
// 文件名: GammaProcessor.cs
// 描述: Gamma校正算子，用于调整图像亮度和对比度
// 功能:
//   - Gamma非线性校正
//   - 增益调整
//   - 使用查找表（LUT）加速处理
//   - 适用于图像显示和亮度调整
// 算法: Gamma校正公式 output = (input^(1/gamma)) * gain
// 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>
/// Gamma校正算子（支持 8 位和 16 位灰度图像）
/// 16 位模式下 LUT 为 ushort[65536]
/// </summary>
public class GammaProcessor<TDepth> : ImageProcessorBase<TDepth>
    where TDepth : struct, IComparable
{
    private static readonly ILogger _logger = Log.ForContext<GammaProcessor<TDepth>>();

    public GammaProcessor()
    {
        Name = LocalizationHelper.GetString("GammaProcessor_Name");
        Description = LocalizationHelper.GetString("GammaProcessor_Description");
    }

    protected override void InitializeParameters()
    {
        Parameters.Add("Gamma", new ProcessorParameter(
            "Gamma",
            LocalizationHelper.GetString("GammaProcessor_Gamma"),
            typeof(double),
            1.0,
            0.1,
            5.0,
            LocalizationHelper.GetString("GammaProcessor_Gamma_Desc")));

        Parameters.Add("Gain", new ProcessorParameter(
            "Gain",
            LocalizationHelper.GetString("GammaProcessor_Gain"),
            typeof(double),
            1.0,
            0.1,
            3.0,
            LocalizationHelper.GetString("GammaProcessor_Gain_Desc")) { IsAdvanced = true });
        _logger.Debug("InitializeParameters");
    }

    public override Image<Gray, TDepth> Process(Image<Gray, TDepth> inputImage)
    {
        double gamma = GetParameter<double>("Gamma");
        double gain = GetParameter<double>("Gain");

        if (typeof(TDepth) == typeof(ushort))
        {
            var lut16 = BuildLUT16(gamma, gain);
            var img16 = inputImage as Image<Gray, ushort>;
            var result = new Image<Gray, ushort>(inputImage.Width, inputImage.Height);
            Parallel.For(0, inputImage.Height, y =>
            {
                for (int x = 0; x < inputImage.Width; x++)
                    result.Data[y, x, 0] = lut16[img16!.Data[y, x, 0]];
            });
            _logger.Debug("Process(16bit): Gamma={G}, Gain={Gain}", gamma, gain);
            return (result as Image<Gray, TDepth>)!;
        }
        else
        {
            var lut8 = BuildLUT8(gamma, gain);
            var result = (inputImage as Image<Gray, byte>)!.Clone();
            int h = inputImage.Height, w = inputImage.Width;
            for (int y = 0; y < h; y++)
                for (int x = 0; x < w; x++)
                    result.Data[y, x, 0] = lut8[result.Data[y, x, 0]];
            _logger.Debug("Process(8bit): Gamma={G}, Gain={Gain}", gamma, gain);
            return (result as Image<Gray, TDepth>)!;
        }
    }

    private static byte[] BuildLUT8(double gamma, double gain)
    {
        var lut = new byte[256];
        double invGamma = 1.0 / gamma;
        for (int i = 0; i < 256; i++)
        {
            double normalized = i / 255.0;
            double corrected = Math.Pow(normalized, invGamma) * gain;
            lut[i] = (byte)Math.Clamp((int)(corrected * 255.0), 0, 255);
        }
        return lut;
    }

    private static ushort[] BuildLUT16(double gamma, double gain)
    {
        var lut = new ushort[65536];
        double invGamma = 1.0 / gamma;
        for (int i = 0; i < 65536; i++)
        {
            double normalized = i / 65535.0;
            double corrected = Math.Pow(normalized, invGamma) * gain;
            lut[i] = (ushort)Math.Clamp((int)(corrected * 65535.0), 0, 65535);
        }
        return lut;
    }
}