C ＃ remove the redundant white part of the picture

        /// <summary>
        ///  Cut the picture （ Remove the edges ）
        /// </summary>
        /// <param name="FilePath"> Picture path </param>
        public void RemoveWhiteEdge(string FilePath)
        {
            Bitmap bmp = new Bitmap(FilePath);
            // Up, down, left, right 
            int top = 0, left = 0, right = bmp.Width, bottom = bmp.Height;
 
            // Look for the top line , From the left (0) To the right , From above (0) Go down 
            for (int i = 0; i < bmp.Height; i++)// That's ok 
            {
                bool find = false;
                for (int j = 0; j < bmp.Width; j++)// Column 
                {
                    Color c = bmp.GetPixel(j, i);
                    if (!IsWhite(c))
                    {
                        top = i;
                        find = true;
                        break;
                    }
                }
                if (find)
                    break;
            }
            // Look for the leftmost line , From above （top position ） Go down , From left to right 
            for (int i = 0; i < bmp.Width; i++)// Column 
            {
                bool find = false;
                for (int j = top; j < bmp.Height; j++)// That's ok 
                {
                    Color c = bmp.GetPixel(i, j);
                    if (!IsWhite(c))
                    {
                        left = i;
                        find = true;
                        break;
                    }
                }
                if (find)
                    break;
            }
            // Find the bottom line , From bottom to top , From left to right 
            for (int i = bmp.Height - 1; i >= 0; i--)// That's ok 
            {
                bool find = false;
                for (int j = left; j < bmp.Width; j++)// Column 
                {
                    Color c = bmp.GetPixel(j, i);
                    if (!IsWhite(c))
                    {
                        bottom = i;
                        find = true;
                        break;
                    }
                }
                if (find)
                    break;
            }
            // Look for the rightmost line , From top to bottom , From right to left 
            for (int i = bmp.Width - 1; i >= 0; i--)// Column 
            {
                bool find = false;
                for (int j = 0; j <= bottom; j++)// That's ok 
                {
                    Color c = bmp.GetPixel(i, j);
                    if (!IsWhite(c))
                    {
                        right = i;
                        find = true;
                        break;
                    }
                }
                if (find)
                    break;
            }
 
            // Clone a part of a bitmap object .
            Rectangle cloneRect = new Rectangle(left, top, right - left, bottom - top);
            Bitmap cloneBitmap = bmp.Clone(cloneRect, bmp.PixelFormat);            
            cloneBitmap.Save(@"D:/service/123.png", ImageFormat.Png);
            bmp.Dispose();           
        }
 
        /// <summary>
        ///  Judge whether white and pure transparent color （10 Tolerance of points ）
        /// </summary>
        public static bool IsWhite(Color c)
        {
            // Pure transparency is also white ,RGB All for 255 Pure white 
            if (c.A < 10 || (c.R > 245 && c.G > 245 && c.B > 245))
                return true;
 
            return false;
        }

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