方法一：直接修改RGB的值

首先将BitmapData扫描线上的所有像素复制到字节数组中，然后遍历数组并对每个像素的RGB值进行修改，最后将修改后的像素值复制回BitmapData。这个过程不会影响原始的Bitmap对象，但会改变锁定的位图区域的数据。当完成修改后，应调用UnlockBits()方法释放锁定的位图区域。
 

System.Drawing.Bitmap bitBufferRGB = new System.Drawing.Bitmap("彩色Bitmap图像.jpg");
System.Drawing.Imaging.BitmapData data = bitBufferRGB.LockBits(
new System.Drawing.Rectangle(System.Drawing.Point.Empty, bitBufferRGB.Size),
System.Drawing.Imaging.ImageLockMode.ReadWrite, bitBufferRGB.PixelFormat);//获取内存
IntPtr pData = data.Scan0;
int bytes = data.Stride * bitBufferRGB.Height;
byte[] rgbValues = new byte[bytes];// Copy the RGB values into the array.
System.Runtime.InteropServices.Marshal.Copy(pData, rgbValues, 0, bytes);for (int y = 0; y < bitBufferRGB.Height; y++)
{for (int x = 0; x < bitBufferRGB.Width; x++){// 获取像素(x, y)在数组中的索引。int index = y * data.Stride + x * 3;// 修改RGB值。rgbValues[index] = (byte)(rgbValues[index] * 0.9); // 修改红色分量rgbValues[index + 1] = (byte)(rgbValues[index + 1] * 0.7); // 修改绿色分量rgbValues[index + 2] = (byte)(rgbValues[index + 2] * 0.9); // 修改蓝色分量}
}// Copy the modified RGB values back to the bitmap.
System.Runtime.InteropServices.Marshal.Copy(rgbValues, 0, pData, bytes);//解锁及释放资源
bitBufferRGB.UnlockBits(data);
bitBufferRGB.Dispose();

方法二：更换RGB的值位置

更换R和B的位置

System.Drawing.Bitmap bitBufferRGB = new System.Drawing.Bitmap("彩色Bitmap图像.jpg");
System.Drawing.Imaging.BitmapData data = bitBufferRGB.LockBits(
new System.Drawing.Rectangle(System.Drawing.Point.Empty, bitBufferRGB.Size),
System.Drawing.Imaging.ImageLockMode.ReadWrite, bitBufferRGB.PixelFormat);//获取内存
IntPtr pData = data.Scan0;
int bytes = data.Stride * bitBufferRGB.Height;
byte[] rgbValues = new byte[bytes];
System.Runtime.InteropServices.Marshal.Copy(pData, rgbValues, 0, bytes);for (int i = 0; i < height; i++)
{for (int ji = 0; ji < width; ji++){int index = i * width + ji;// 每个像素占用三个字节// 红色字节rgbValues[index * 3] = System.Runtime.InteropServices.Marshal.ReadByte(pData, index * 3 + 2);// 绿色字节rgbValues[index * 3 + 1] = System.Runtime.InteropServices.Marshal.ReadByte(pData, index * 3 + 1);// 蓝色字节rgbValues[index * 3 + 2] = System.Runtime.InteropServices.Marshal.ReadByte(pData, index * 3);}
}
System.Runtime.InteropServices.Marshal.Copy(rgbValues, 0, pData, bytes);//解锁及释放资源
bitBufferRGB.UnlockBits(data);
bitBufferRGB.Dispose();