从文件中裁剪图像并在C#中重新保存

以前从未真正使用过Graphics。我环顾四周，从回答我问题的小部分中拼凑出了一些解决方案。但都没有奏效。

我想从文件中加载一个图像，该文件的大小将始终为320x240。然后我想裁剪它以获得240x240的图像，每侧的外部40px都经过修剪。完成后，我想保存为一个新的图像。

    private void croptoSquare(string date)
    {
        //Location of 320x240 image
        string fileName = Server.MapPath("~/Content/images/" + date + "contactimage.jpg");
        //New rectangle of final size (I think maybe Point is where I would eventually specify where the crop square site i.e. (40, 0))
        Rectangle cropRect = new Rectangle(new Point(0, 0), new Size(240, 240));
        //Create a Bitmap with correct height/width.
        Bitmap target = new Bitmap(cropRect.Width, cropRect.Height);
        //Load image from file
        using (Image image = Image.FromFile(fileName))
        {
            //Create Graphics object from image
            using (Graphics graphic = Graphics.FromImage(image))
            {
                //Not sure what this does, I found it on a post.
                graphic.DrawImage(image, 
                    cropRect, 
                    new Rectangle(0, 0, target.Width, target.Height),
                    GraphicsUnit.Pixel);
                fileName = Server.MapPath("~/Content/images/" + date + "contactimagecropped.jpg");
                image.Save(fileName);
            }
        }
    }

目前，它只是重新保存相同的图像，我不知道为什么。我已经将目标矩形指定为240x240，将src矩形指定为320x240。

正如我所说，我基本上对处理图形对象一无所知，所以我认为这是公然的。

有人能告诉我如何实现我想要的吗？

private void croptoSquare(string date)
{
    //Location of 320x240 image
    string fileName = Server.MapPath("~/Content/images/" + date + "contactimage.jpg");
    // Create a new image at the cropped size
    Bitmap cropped = new Bitmap(240,240);
    //Load image from file
    using (Image image = Image.FromFile(fileName))
    {
        // Create a Graphics object to do the drawing, *with the new bitmap as the target*
        using (Graphics g = Graphics.FromImage(cropped) )
        {
            // Draw the desired area of the original into the graphics object
            g.DrawImage(image, new Rectangle(0, 0, 240, 240), new Rectangle(40, 0, 240, 240), GraphicsUnit.Pixel);
            fileName = Server.MapPath("~/Content/images/" + date + "contactimagecropped.jpg");
            // Save the result
            cropped.Save(fileName);  
        }
     }
}