Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
Resizing your image introduces new colors and promotes the image from colormapped to truecolor. To solve the problem, either use -sample to resize or add -colors 256 to your command line to change the image back to colormapped before writing it.