Any field may be read or written as a string, and the usual type conversions are permitted for the numeric data types. It is an error to attempt to delete a nonexistent field. The template is expanded upon an image header rather than a directory. Unsorted lists are the most useful for image header fields. If sorting is enabled each comma delimited pattern in the template is sorted separately, rather than globally sorting the entire template after expansion.
Minimum match is permitted when expanding the template, another difference from file templates.
Only actual, full length field names are placed in the output list. In addition, there may be other parameters unique to the particular image. It is however recommended that the full name be used in all applications software. This defines macros for standard image header parameters dealing with fundamental characteristics of the image such as the size, data type, etc. Others may be accessed through the imio database procedures.