WPF在使用Graphics.CopyFromScreen截图时，截到的图片与输入的坐标不一致

                var bitmap = new Bitmap((int)width, (int)height, PixelFormat.Format32bppArgb);

                using (Graphics memoryGrahics = Graphics.FromImage(bitmap))
                {
                    memoryGrahics.CopyFromScreen((int)left, (int)top, 0, 0, new Size((int)width, (int)height), CopyPixelOperation.SourceCopy);                   

                }
                return bitmap;                var bitmap = new Bitmap((int)wi