我如何转换我的GetPixel / SetPixel颜色处理Lockbits

编辑:我非常感谢您的回复。这里我最需要的是示例代码，用于我在嵌套循环中使用几行代码所做的事情，因为这是在GetPixel/SetPixel中正确工作的，但也是我无法使用Lockbits正确工作的。谢谢你

我正试图将我的图像处理过滤器从GetPixel/SetPixel转换为Lockbits，以提高处理时间。我在堆栈溢出，MSDN和其他网站上也看到了Lockbits教程，但我做错了什么。我从一个非常简单的过滤器开始，它简单地减少绿色来创建红色和紫色的效果。下面是我的代码:

   private void redsAndPurplesToolStripMenuItem_Click(object sender, EventArgs e)
    {
        // Get bitmap from picturebox
        Bitmap bmpMain = (Bitmap)pictureBoxMain.Image.Clone();
        // search through each pixel via x, y coordinates, examine and make changes. Dont let values exceed 255 or fall under 0.  
        for (int y = 0; y < bmpMain.Height; y++)
            for (int x = 0; x < bmpMain.Width; x++)
            {
                bmpMain.GetPixel(x, y);
                Color c = bmpMain.GetPixel(x, y);
                int myRed = c.R, myGreen = c.G, myBlue = c.B;
                myGreen -= 128;
                if (myGreen < 0) myGreen = 0; 
                bmpMain.SetPixel(x, y, Color.FromArgb(255, myRed, myGreen, myBlue));
            }
        // assign the new bitmap to the picturebox
        pictureBoxMain.Image = (Bitmap)bmpMain;
        // Save a copy to the HD for undo / redo.
        string myString = Environment.GetEnvironmentVariable("temp", EnvironmentVariableTarget.Machine);
        pictureBoxMain.Image.Save(myString + "''ColorAppRedo.png", System.Drawing.Imaging.ImageFormat.Png);
    }

所以GetPixel/SetPixel代码工作得很好，但它很慢。所以我试着这样做:

    private void redsAndPurplesToolStripMenuItem_Click(object sender, EventArgs e)
    {
        // Get bitmap from picturebox
        Bitmap bmpMain = (Bitmap)pictureBoxMain.Image.Clone();
        Rectangle rect = new Rectangle(Point.Empty, bmpMain.Size); 
        BitmapData bmpData = bmpMain.LockBits(rect, ImageLockMode.ReadOnly, bmpMain.PixelFormat); 
        // search through each pixel via x, y coordinates, examine and make changes. Dont let values exceed 255 or fall under 0.  
        for (int y = 0; y < bmpMain.Height; y++)
            for (int x = 0; x < bmpMain.Width; x++)
            {
                bmpMain.GetPixel(x, y);
                Color c = new Color(); 
                int myRed = c.R, myGreen = c.G, myBlue = c.B;
                myGreen -= 128;
                if (myGreen < 0) myGreen = 0; 
                bmpMain.SetPixel(x, y, Color.FromArgb(255, myRed, myGreen, myBlue));
            }
        bmpMain.UnlockBits(bmpData); 
        // assign the new bitmap to the picturebox
        pictureBoxMain.Image = (Bitmap)bmpMain;
        // Save a copy to the HD for undo / redo.
        string myString = Environment.GetEnvironmentVariable("temp", EnvironmentVariableTarget.Machine);
        pictureBoxMain.Image.Save(myString + "''ColorAppRedo.png", System.Drawing.Imaging.ImageFormat.Png);
    } 

抛出错误"类型为'System '的未处理异常"。附加信息:位图区域已被锁定"当它到达嵌套循环的第一行时。

我意识到这必须是一个初学者的错误，如果有人能演示正确的方式将这个非常简单的过滤器转换为Lockbits，我会很感激。非常感谢

BGRA BGRA BGRA BGRA
BGRA BGRA BGRA BGRA
BGRA BGRA BGRA BGRA 
stride = width*bytesPerPixel = 4*4 = 16 bytes
height = 3
maxLenght = stride*height= 16*3 = 48 bytes

int certainPixel = bytesPerPixel*x + stride * y;
B = scan0[certainPixel + 0];
G = scan0[certainPixel + 1];
R = scan0[certainPixel + 2];
A = scan0[certainPixel + 3];

    public unsafe void Test(Bitmap bmp)
    {
        int width = bmp.Width;
        int height = bmp.Height;
        //TODO determine bytes per pixel
        int bytesPerPixel = 4; // we assume that image is Format32bppArgb
        int maxPointerLenght = width * height * bytesPerPixel;
        int stride = width * bytesPerPixel;
        byte R, G, B, A;
        BitmapData bData = bmp.LockBits(
            new System.Drawing.Rectangle(0, 0, bmp.Width, bmp.Height),
            ImageLockMode.ReadWrite, bmp.PixelFormat);

        byte* scan0 = (byte*)bData.Scan0.ToPointer();
        for (int i = 0; i < maxPointerLenght; i += 4)
        {
            B = scan0[i + 0];
            G = scan0[i + 1];
            R = scan0[i + 2];
            A = scan0[i + 3];
            // do anything with the colors
            // Set the green component to 0
            G = 0;
            // do something with red
            R = R < 54 ? (byte)(R + 127) : R;
            R = R > 255 ? 255 : R;
        }

        bmp.UnlockBits(bData);
    }

 ... = bmpMain.LockBits(rect, ImageLockMode.ReadOnly, bmpMain.PixelFormat);