When attempting to open an image file where the extension indicates a particular file type, but the file is of a different image type, the program crashes. When fullscreened, there is no way to exit the program without sending it a console interrupt or kill command (at least in Linux).
For example, if an image is opened that has a png extension, but the headers indicate JPEG image data, JFIF standard 1.01
(using the file
command on Linux), the following is printed in the console, and no image displays:
TApplication.HandleException Wrong image format
With a stack trace that includes only hexadecimal values (not included because I do not know what information it contains)
Most image viewer software will use the extension only to indicate if it should try to open the file, while the header information is used to determine how to interpret the information.