QUERY_PPM is a method of obtaining information about a PPM image file without having to read the file. See QUERY_* Routines for more information.
Result = QUERY_PPM ( Filename [, Info] [, MAXVAL=variable] )
This routine returns a long with the value of 1 (one) if the query was successful (and the file type was correct) or 0 (zero) on failure.
A scalar string containing the pathname of the PPM file to query.
Returns an anonymous structure containing information about the image. The Info.TYPE field will return the value ‘PPM’.
Additional field in the Info structure: MAXVAL - maximum pixel value in the image.
Note: See General Query * Routine Info Structures for detailed structure information.
Set this keyword to a named variable to retrieve the maximum pixel value in the image.
QUERY_* Routines, READ_PPM, WRITE_PPM