//图片路径
String oldPath = Server.MapPath("~/62223231.jpg");
//新图片路径
String newPath = System.IO.Path.GetExtension(oldPath);
//设置截取的坐标和大小
int x = 0, y = 20, width = 200, height = 2400;
//计算新的文件名，在旧文件名后加_new
newPath = oldPath.Substring(0, oldPath.Length - newPath.Length) + "_new" + newPath;
Response.Write(oldPath);
Response.Write("<br>");
Response.Write(newPath);
//定义截取矩形
System.Drawing.Rectangle cropArea = new System.Drawing.Rectangle(x, y, width, height); //要截取的区域大小
//加载图片
System.Drawing.Image img = System.Drawing.Image.FromStream(new System.IO.MemoryStream(System.IO.File.ReadAllBytes(oldPath)));
//判断超出的位置否
if ((img.Width < x + width) || img.Height < y + height)
{
 Response.Write("截取的区域超过了图片本身的高度、宽度.");
 img.Dispose();
 return;
}
//定义Bitmap对象
System.Drawing.Bitmap bmpImage = new System.Drawing.Bitmap(img);
//进行裁剪
System.Drawing.Bitmap bmpCrop = bmpImage.Clone(cropArea, bmpImage.PixelFormat);
//保存成新文件
bmpCrop.Save(newPath);
//释放对象
img.Dispose();
bmpCrop.Dispose();