图片反转

            if (_srcBitmap != null) //_srcBitmap = (Bitmap)Image.FromFile(_curFileName)
            {
                _dstBitmap = (Bitmap)_srcBitmap.Clone();
                BitmapData bmpData = _srcBitmap.LockBits(new Rectangle(0, 0, _srcBitmap.Width, _srcBitmap.Height),ImageLockMode.ReadWrite, _srcBitmap.PixelFormat);
                BitmapData dstData = _dstBitmap.LockBits(new Rectangle(0, 0, _dstBitmap.Width, _dstBitmap.Height),ImageLockMode.ReadWrite, _dstBitmap.PixelFormat);
                unsafe
                {
                    byte* p = (byte*)bmpData.Scan0;
                    for (int y = 0; y < bmpData.Height; y++)
                    {
                        for (int x = 0; x < bmpData.Width; x++)
                        {
                            byte* dstp = (byte*)dstData.Scan0 + y * dstData.Stride + x * 3;
                            dstp[0] = p[bmpData.Width * 3 - (x + 1) * 3];
                            dstp[1] = p[bmpData.Width * 3 - (x + 1) * 3 + 1];
                            dstp[2] = p[bmpData.Width * 3 - (x + 1) * 3 + 2];
                        }
                        p += bmpData.Stride;    //Stride 为扫描宽度 Stride > bmpData.Width * 3 ,Width 表示每行的像素个数，每个像素占3个byte位
                    }
                    _srcBitmap.UnlockBits(bmpData);
                    _dstBitmap.UnlockBits(dstData);
                }
                _srcBitmap = (Bitmap)_dstBitmap.Clone();
                Invalidate();
            }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            if (_srcBitmap != null)
            {
                g.DrawImage(_srcBitmap, 10, 30, _srcBitmap.Width, _srcBitmap.Height);
            }
        }

        private Bitmap gcTrans(Bitmap bmp, bool method, byte seg)
        {
            if (bmp != null)
            {
                if (System.Drawing.Imaging.PixelFormat.Format24bppRgb == bmp.PixelFormat)
                {
                    Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
                    System.Drawing.Imaging.BitmapData bmpData = bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite, bmp.PixelFormat);
                    IntPtr ptr = bmpData.Scan0;
                    int bytes = bmp.Width * bmp.Height * 3;
                    byte[] grayValues = new byte[bytes];
                    System.Runtime.InteropServices.Marshal.Copy(ptr, grayValues, 0, bytes);
                    bmp.UnlockBits(bmpData);
                    byte[] rgbValues = new byte[bytes];
                    //清零
                    Array.Clear(rgbValues, 0, bytes);
                    byte tempB;
                    if (method == false)
                    {
                        //强度分层法
                        for (int i = 0; i < bytes; i += 3)
                        {
                            byte ser = (byte)(256 / seg);
                            tempB = (byte)(grayValues[i] / ser);
                            //分配任意一种颜色
                            rgbValues[i + 1] = (byte)(tempB * ser);
                            rgbValues[i] = (byte)((seg - 1 - tempB) * ser);
                            rgbValues[i + 2] = 0;
                        }
                    }
                    else
                    {
                        //灰度级-彩色变换法
                        for (int i = 0; i < bytes; i += 3)
                        {
                            if (grayValues[i] < 64)
                            {
                                rgbValues[i + 2] = 0;
                                rgbValues[i + 1] = (byte)(4 * grayValues[i]);
                                rgbValues[i] = 255;
                            }
                            else if (grayValues[i] < 128)
                            {
                                rgbValues[i + 2] = 0;
                                rgbValues[i + 1] = 255;
                                rgbValues[i] = (byte)(-4 * grayValues[i] + 2 * 255);
                            }
                            else if (grayValues[i] < 192)
                            {
                                rgbValues[i + 2] = (byte)(4 * grayValues[i] - 2 * 255);
                                rgbValues[i + 1] = 255;
                                rgbValues[i] = 0;
                            }
                            else
                            {
                                rgbValues[i + 2] = 255;
                                rgbValues[i + 1] = (byte)(-4 * grayValues[i] + 4 * 255);
                                rgbValues[i] = 0;
                            }
                        }
                    }
                    bmp = new Bitmap(bmp.Width, bmp.Height, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
                    bmpData = bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite, bmp.PixelFormat);
                    ptr = bmpData.Scan0;
                    System.Runtime.InteropServices.Marshal.Copy(rgbValues, 0, ptr, bytes);
                    bmp.UnlockBits(bmpData);
                    return bmp;
                }
                else
                {
                    return null;
                }
            }
            else
            {
                return null;
            }
        }