CaptchaRecogition.ImageProcess.GetPicValidByValue C# (CSharp) Метод

        public static Bitmap GetPicValidByValue(Bitmap singlepic, int dgGrayValue)
        {
            int posx1 = singlepic.Width;
            int posy1 = singlepic.Height;
            int posx2 = 0;
            int posy2 = 0;
            for (int i = 0; i < singlepic.Height; i++) //找有效区
            {
                for (int j = 0; j < singlepic.Width; j++)
                {
                    int pixelValue = singlepic.GetPixel(j, i).R;
                    if (pixelValue < dgGrayValue) //根据灰度值
                    {
                        if (posx1 > j) posx1 = j;
                        if (posy1 > i) posy1 = i;

                        if (posx2 < j) posx2 = j;
                        if (posy2 < i) posy2 = i;
                    }

                }

            }

            //复制新图
            Rectangle cloneRect = new Rectangle(posx1, posy1, posx2 - posx1 + 1, posy2 - posy1 + 1);
            return singlepic.Clone(cloneRect, singlepic.PixelFormat);
        }