using OpenCvSharp;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace PaintDotNet.Adjust
{
    /// <summary>
    /// 曝光处理
    /// </summary>
    public unsafe class ExposedIntent
    {
        private static int underExposedPixel = 0;//曝光不足像素阈值
        private static int overExposedPixel = 0;//过曝光像素阈值
        private static float ratio = 0;//占总像素点比例
        private static Mat exposedMat;//全局mat对象
        private static float underPixelCount = 0;//过暗像素点个数
        private static float overPixelCount = 0;//过亮像素点个数
        private static float allPixelCount = 0;//总像素点个数

        /// <summary>
        /// 判断曝光状态并返回对应像素点数量
        /// </summary>
        /// <param name="src"></param>
        /// <returns></returns>
        public static void ExposureState(Mat src)
        {
            //配置输出的结果存储的 空间 ，用MatND类型来存储结果
            Mat hist = new Mat();
            //设置计算的维度
            int dims = 1;
            //每一个维度的柱条的数目(就是将数值分组，共有多少组)
            int[] histSize = { 256 };
            Rangef[] pranges = new Rangef[1];//一个通道，范围
            pranges[0] = new Rangef(0.0F, 256.0F);
            Mat grayMat = src.CvtColor(ColorConversionCodes.BGRA2GRAY);//转换为灰度图
            //计算直方图
            Cv2.CalcHist(new Mat[1] { grayMat }, new int[] { 0 }, new Mat(), hist, dims, histSize, pranges);

            //循环记录像素点
            for (int i = 0; i < hist.Height; i++)
            {
                for (int j = 0; j < hist.Width; j++)
                {
                    float pixelCount = hist.At<float>(i, j);
                    allPixelCount += pixelCount;
                    if (i < underExposedPixel && underExposedPixel != 0)
                        underPixelCount += pixelCount;
                    if (i > overExposedPixel && overExposedPixel != 0)
                        overPixelCount += pixelCount;
                }
            }
        }

        /// <summary>
        /// 曝光不足,替换像素点为蓝色
        /// </summary>
        /// <param name="src"></param>
        /// <param name="underExposedPixel">曝光不足像素阈值</param>
        /// <param name="ratio">占总像素点比例</param>
        /// <returns></returns>
        public static Mat UnderExposed(Mat src, int thresholdvalue, float exposedRatio)
        {
            underExposedPixel = thresholdvalue;
            ratio = exposedRatio;
            exposedMat = src;

            ExposureState(src);

            //判断过暗,如果阈值内的像素点多余总像素点一定比例
            if (underPixelCount > 0)
            {
                if (underPixelCount / allPixelCount > ratio)
                {
                    Mat grayMat = src.CvtColor(ColorConversionCodes.BGRA2GRAY);//转换为灰度图
                    grayMat.ForEachAsByte(ForeachFunctionUnderExposedByte);
                }
            }
            
            return exposedMat;
        }

        /// <summary>
        /// 过曝光,替换像素点为红色
        /// </summary>
        /// <param name="src"></param>
        /// <param name="overExposedPixel">过曝光像素阈值</param>
        /// <param name="ratio">占总像素点比例</param>
        /// <returns></returns>
        public static Mat OverExposed(Mat src, int thresholdvalue, float exposedRatio)
        {
            overExposedPixel = thresholdvalue;
            ratio = exposedRatio;
            exposedMat = src;

            ExposureState(src);

            //判断过亮,如果阈值内的像素点多余总像素点一定比例
            if (overPixelCount > 0)
            {
                if (overPixelCount / allPixelCount > ratio)
                {
                    Mat grayMat = src.CvtColor(ColorConversionCodes.BGRA2GRAY);//转换为灰度图
                    grayMat.ForEachAsByte(ForeachFunctionOverExposedByte);
                }
            }
            
            return exposedMat;
        }

        /// <summary>
        /// 更高效的循环替换方法-曝光不足
        /// </summary>
        /// <param name="t"></param>
        /// <param name="position"></param>
        public unsafe static void ForeachFunctionUnderExposedByte(byte* t, int* position)
        {
            int y = position[0];
            int x = position[1];

            if (*t < underExposedPixel)
            {
                exposedMat.Set<Vec3b>(y, x, new Vec3b(255, 0, 0));//改为蓝色
            }
        }

        /// <summary>
        /// 更高效的循环替换方法-过曝光
        /// </summary>
        /// <param name="t"></param>
        /// <param name="position"></param>
        public unsafe static void ForeachFunctionOverExposedByte(byte* t, int* position)
        {
            int y = position[0];
            int x = position[1];

            if (*t > overExposedPixel)
            {
                exposedMat.Set<Vec3b>(y, x, new Vec3b(0, 0, 255));//改为红色
            }
        }

    }
}