Image.Save Method (Stream, ImageFormat)
Saves this image to the specified stream in the specified format.
Assembly: System.Drawing (in System.Drawing.dll)
You should avoid saving an image to the same stream that was used to construct it. Doing so might damage the stream.
The image must be saved to the stream at an offset of zero. If any additional data has been written to the stream before saving the image, the image data in the stream will be corrupted.