Questions and postings pertaining to the development of ImageMagick, feature enhancements, and ImageMagick internals. ImageMagick source code and algorithms are discussed here. Usage questions which are too arcane for the normal user list should also be posted here.
ImageMagick tries to determine what file format an image is in but can't always succeed. If the magic number does not confirm its format it tries to use the file extension (.ico means the image is in the ICO format). You can always force a format. For example,