c#文档图片自动纠偏

        // The Bitmap
        public Bitmap _internalBmp;

        // The range of angles to search for lines
        const double ALPHA_START = -20;
        const double ALPHA_STEP = 0.2;
        const int STEPS = 40 * 5;
        const double STEP = 1;

        // Precalculation of sin and cos.
        double[] _sinA;
        double[] _cosA;

        // Range of d
        double _min;

        int _count;
        // Count of points that fit in a line.
        int[] _hMatrix;

        // Calculate the skew angle of the image cBmp.
        public double GetSkewAngle()
        {
            // Hough Transformation
            Calc();

            // Top 20 of the detected lines in the image.
            HougLine[] hl = GetTop(20);

            // Average angle of the lines
            double sum = 0;
            int count = 0;
            for (int i = 0; i <= 19; i++)
            {
                sum += hl[i].Alpha;
                count += 1;
            }
            return sum / count;
        }

        // Calculate the Count lines in the image with most points.
        private HougLine[] GetTop(int count)
        {
            HougLine[] hl = new HougLine[count];

            for (int i = 0; i <= count - 1; i++)
            {
                hl[i] = new HougLine();
            }
            for (int i = 0; i <= _hMatrix.Length - 1; i++)
            {
                if (_hMatrix[i] > hl[count - 1].Count)
                {
                    hl[count - 1].Count = _hMatrix[i];
                    hl[count - 1].Index = i;
                    int j = count - 1;
                    while (j > 0 && hl[j].Count > hl[j - 1].Count)
                    {
                        HougLine tmp = hl[j];
                        hl[j] = hl[j - 1];
                        hl[j - 1] = tmp;
                        j -= 1;
                    }
                }
            }

            for (int i = 0; i <= count - 1; i++)
            {
                int dIndex = hl[i].Index / STEPS;
                int alphaIndex = hl[i].Index - dIndex * STEPS;
                hl[i].Alpha = GetAlpha(alphaIndex);
                //hl[i].D = dIndex + _min;
            }

            return hl;
        }

        // Hough Transforamtion:
        private void Calc()
        {
            int hMin = _internalBmp.Height / 4;
            int hMax = _internalBmp.Height * 3 / 4;

            Init();
            for (int y = hMin; y