C#掃描圖片去黑邊

最近項目遇到一個問題，需要對掃描出來的圖片進行去除黑邊。百度下沒有找到處理黑邊的源碼，無奈自己嘗試寫了這個方法。

        /// <summary>
        /// 自動去除圖像掃描黑邊
        /// </summary>
        /// <param name="fileName"></param>
        public static void AutoCutBlackEdge(string fileName)
        {
            //打開圖像
            Bitmap bmp = OpenImage(fileName);

            RemoveBlackEdge(bmp);
            //保存圖像
            SaveImage(bmp, fileName);
        }

        private static byte[] rgbValues; // 目標數組內存

        /// <summary>
        /// 圖像去黑邊
        /// </summary>
        /// <param name="bmp"></param>
        /// <returns></returns>
        private static Bitmap RemoveBlackEdge(Bitmap bmp)
        {
            Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
            BitmapData bmpData = bmp.LockBits(rect, ImageLockMode.ReadWrite, bmp.PixelFormat);

            // 獲取圖像參數  
            int w = bmpData.Width;
            int h = bmpData.Height;
            int stride = bmpData.Stride;  // 掃描線的寬度 
            double picByteSize = GetPicByteSize(bmp.PixelFormat);
            int bWidth = (int)Math.Ceiling(picByteSize * w); //顯示寬度
            int offset = stride - bWidth;  // 顯示寬度與掃描線寬度的間隙  
            IntPtr ptr = bmpData.Scan0;   // 獲取bmpData的內存起始位置  
            int scanBytes = stride * h;  // 用stride寬度，表示這是內存區域的大小

            // 分別設置兩個位置指針，指向源數組和目標數組  
            int posScan = 0;
            rgbValues = new byte[scanBytes];  // 為目標數組分配內存  
            Marshal.Copy(ptr, rgbValues, 0, scanBytes);  // 將圖像數據拷貝到rgbValues中  

            bool isPass = true;
            int i = 0, j = 0;
            int cutW = (int)(bWidth * 0.02); //2%寬度（可修改）
            int cutH = (int)(h * 0.02);      //2%高度（可修改）
            int posLen = (int)(picByteSize * 8); //繼續查找深度為8的倍數（可修改）
            //左邊
            for (i = 0; i < h; i++)
            {
                for (j = 0; j < bWidth; j++)
                {
                    isPass = true;
                    if (rgbValues[posScan] < 255) rgbValues[posScan] = 255;

                    if (rgbValues[posScan + 1] == 255)
                    {
                        for (int m = 1; m <= posLen; m++)
                        {
                            if (rgbValues[posScan + m] < 255) isPass = false;
                        }
                    }
                    if (rgbValues[posScan + 1] < 255 || bWidth / 2 < j) isPass = false;
                    recCheck(ref rgbValues, posScan, h, stride, true);

                    posScan++;
                    if (j >= cutW && isPass) break;
                }
                // 跳過圖像數據每行未用空間的字節，length = stride - width * bytePerPixel  
                if (j == bWidth) posScan += offset;
                else posScan += (offset + bWidth - j - 1);
            }
            //右邊
            posScan = scanBytes - 1;
            for (i = h - 1; i >= 0; i--)
            {
                posScan -= offset;
                for (j = bWidth - 1; j >= 0; j--)
                {
                    isPass = true;
                    if (rgbValues[posScan] < 255) rgbValues[posScan] = 255;

                    if (rgbValues[posScan - 1] == 255)
                    {
                        for (int m = 1; m <= posLen; m++)
                        {
                            if (rgbValues[posScan - m] < 255) isPass = false;
                        }
                    }
                    if (rgbValues[posScan - 1] < 255 || bWidth / 2 > j) isPass = false;
                    recCheck(ref rgbValues, posScan, h, stride, false);

                    posScan--;
                    if (cutH < (h - i))
                        if (j < (bWidth - cutW) && isPass) break;
                }
                // 跳過圖像數據每行未用空間的字節，length = stride - width * bytePerPixel
                if (j != -1) posScan -= j;
            }

            // 內存解鎖  
            Marshal.Copy(rgbValues, 0, ptr, scanBytes);
            bmp.UnlockBits(bmpData);  // 解鎖內存區域  

            return bmp;
        }

        /// <summary>
        /// 上下去除黑邊時，臨近黑點去除
        /// </summary>
        /// <param name="rgbValues"></param>
        /// <param name="posScan"></param>
        /// <param name="h"></param>
        /// <param name="stride"></param>
        /// <param name="islLeft"></param>
        private static void recCheck(ref byte[] rgbValues, int posScan, int h, int stride, bool islLeft)
        {
            int scanBytes = h * stride;
            int cutH = (int)(h * 0.01); //臨近最大1%高度（可修改）
            for (int i = 1; i <= cutH; i++)
            {
                int befRow = 0;
                if (islLeft && (posScan - stride * i) > 0)
                {
                    befRow = posScan - stride * i;
                }
                else if (!islLeft && (posScan + stride * i) < scanBytes)
                {
                    befRow = posScan + stride * i;
                }
                if (rgbValues[befRow] < 255) rgbValues[befRow] = 255;
                else break;
            }
        }    

該方法沒有涉及到什么算法，都是按自己的思路寫的。雖然還是存在缺陷，但對於一般的文檔黑邊，還是夠用的。歡迎大家進行擴展或修改，並多多指點。

/// <summary>
/// 根據圖片像素數據格式獲得占的字節大小
/// </summary>
/// <param name="bmpPixelFormat"></param>
/// <returns></returns>
private static double GetPicByteSize(PixelFormat bmpPixelFormat)
{
double picByteSize;
if (bmpPixelFormat == PixelFormat.Format24bppRgb) picByteSize = 3;
else if (bmpPixelFormat == PixelFormat.Format32bppArgb) picByteSize = 4;
else if (bmpPixelFormat == PixelFormat.Format8bppIndexed) picByteSize = (double)3 / 24 * 8;
else if (bmpPixelFormat == PixelFormat.Format1bppIndexed) picByteSize = (double)3 / 24;
else if (bmpPixelFormat == PixelFormat.Format4bppIndexed) picByteSize = (double)3 / 24 * 4;
else picByteSize = 3;

return picByteSize;
}