截图片

 public static Image CutImage(Image img, int width, int height)
        {
            Bitmap image = new Bitmap(img);

            int calheight = width * image.Height / image.Width;
            int calwidth = height * image.Width / image.Height;

            Image img2;

            if (calheight >= height)
            {
                img2 = image.GetThumbnailImage(width, calheight, null, IntPtr.Zero);
            }
            else
            {
                img2 = image.GetThumbnailImage(calwidth, height, null, IntPtr.Zero);
            }

            Bitmap bitmap = new Bitmap(img2);
            int x = (bitmap.Width - width) / 2;
            int y = (bitmap.Height - height) / 2;
            Rectangle cloneRect = new Rectangle(x, y, width, height);
            PixelFormat format = bitmap.PixelFormat;
            Bitmap cloneBitmap = bitmap.Clone(cloneRect, format);

            return cloneBitmap;

        }