I am loading an image file into an ImageEnView. That image has an unknown file extension (e.g. .MyUnknownExt). So ImageEnView must detect itself what real image type the file is (.png or .jpg or .gif etc.).
Then ImageEnView mus get the comment metadata string from that image file. Then ImageEnView must MODIFY the found comment metadata string or create a new one. Then ImageEnView must save the file using the same .MyUnknownExt file extension but maintaining the same image file type (.png or .jpg or .gif etc.).