WPF：圖像處理（五）疊代法

using System;

namespace Splash.Imaging
{
    /// <summary>
    /// 圖像處理：疊代法二值化門檻值計算方法
    /// </summary>
    public static partial class Binarize
    {
        /// <summary>
        /// 疊代法計算門檻值
        /// </summary>
        /// <param name="grayArray">灰階數組</param>
        /// <returns>二值化門檻值</returns> 
        public static Int32 IterativeThreshold(Byte[,] grayArray)
        {   // 建立統計直方圖
            Int32[] Histogram = new Int32[256];
            Array.Clear(Histogram, 0, 256);     // 初始化
            foreach (Byte b in grayArray)
            {
                Histogram[b]++;                 // 統計直方圖
            }

            // 總的品質矩和圖像點數
            Int32 SumC = grayArray.Length;    // 總的圖像點數
            Int32 SumU = 0;
            for (Int32 i = 1; i < 256; i++)
            {
                SumU += i * Histogram[i];     // 總的品質矩                
            }

            // 确定初始門檻值
            Int32 MinGrayLevel = Array.FindIndex(Histogram, NonZero);       // 最小灰階值
            Int32 MaxGrayLevel = Array.FindLastIndex(Histogram, NonZero);   // 最大灰階值
            Int32 T0 = (MinGrayLevel + MaxGrayLevel) >> 1;
            if (MinGrayLevel != MaxGrayLevel)
            {
                for (Int32 Iteration = 0; Iteration < 100; Iteration++)
                {   // 計算目标的品質矩和點數
                    Int32 U0 = 0;
                    Int32 C0 = 0;
                    for (Int32 i = MinGrayLevel; i <= T0; i++)
                    {   // 目标的品質矩和點數                
                        U0 += i * Histogram[i];
                        C0 += Histogram[i];
                    }

                    // 目标的平均灰階值和背景的平均灰階值的中心值
                    Int32 T1 = (U0 / C0 + (SumU - U0) / (SumC - C0)) >> 1;
                    if (T0 == T1) break; else T0 = T1;
                }
            }

            // 傳回最佳門檻值
            return T0;
        }        
    }
}